"...If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability."
Read it again. The "it" that is the second word in this sentence refers to the creature whose spell you are trying to counter. Is that what you misunderstood?
There is no confusion as to what "it" is... I used several examples to properly iterate and illustrate the proper understanding of the word "it." The issue in contention is people think that upcasting has no added value -- or change in outcome. People are saying that it's simply pass or fail, however, the 3rd sentence explicitly states an ability check must be made for 4th or higher for when "it" the spell isn't automatically, countered. WHAT IS THAT FORMULA?
But if the spell is automatically countered by the higher level casting there's no point in doing the check.
You only make the check if the spell has not already been automatically countered.
If it is not automatically countered -- How do you perform the ability check. What is the calculation? What is the formula? DC='s 10+ ???
The forumla for the DC remains the same: 10 + the level of the spell you're trying to counter.
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Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond. Need help with Homebrew? Check out ✨ thisFAQ/Guide thread ✨ by IamSposta.
What is the calculation? Well here is the formula that you can plug into Excel/Sheets/Openoffice:
IF (counterspell_spell_slot_level, >= target_spell_slot_level, DC=0,DC=10+target_spell_slot_level)
Make Column A counterspell_spell_slot_level. Make column B target_spell_slot_level. Make column C DC. Make column D ability_modifier. Make column E minimum roll needed. Since on ability checks 1's do not automatically fail, a DC of 0 represents automatic success. The DC formula would then look like the following: =IF(A2>=B2,0,10+B2) and the minimum roll needed would be =IF(C2-D2>0,C2-D2,1)
The base casting of the spell calls for a skill check specifically at 4th level, because it's a 3rd a level spell by default. But the required spell level trigger for requiring a skill check is changed based on the text found in casting at higher levels.
@OP: There are 5 people trying to tell you that you are over complicating the interpretation of this spell.
You attempt to interrupt a creature in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect (Because the lowest level Counterspell can be cast is level 3. Therefore the Counterspell you cast is equal to or greater than the spell being cast by the other creature). If it (the creature) is casting a spell of 4th level or higher, make an ability check using your spellcasting ability(ie: when you're casting it at level 3). The DC equals 10 + the spell's level (of the spell being cast by the creature). On a success(if you succeed the check), the creature's spell fails and has no effect.
At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the interrupted spell has no effect if its level(its level = the interrupted spell) is less than or equal to the level of the spell slot you used. (ie: if the creature casts a level 4 spell, and you cast a level 4 or greater counterspell, no check is required. If the creature casts a level 7 spell and you cast a level 7 or greater counterspell, no check is required. Etc...)
1) The DC for the ability check IS 10+ (the level of the spell you are trying to counter)
2) You only need to make an ability check IF the spell slot level you used for counterspell is less than the level of the spell you are trying to counter. If you use a spell slot for counterspell that is equal to or greater than the level of the spell you are trying to counter then you automatically succeed.
If the DC is required it is always 10+ (the level of the spell you are trying to counter)
If someone uses a 5th level slot to cast a fireball, the DC, IF required will be 15. The DC is ONLY required if you cast counterspell with a 4th level or lower slot.
---
You may ask why this matters .. in many games when someone (either the NPCs or the players have counterspell), all the player or DM says is that they are casting a spell since that is typically all that is known at the time the spell is cast. Neither players nor NPCs know what spell is being cast or what spell level it is being cast at. As a result, the player (or NPC) has to consider or guess what level of spell slot to use for counterspell since to automatically counter the spell they need to use a slot equal to or greater than the spell being cast.
If they fail to choose the correct level for the counterspell or they don't have a high enough level spell slot then they have to make an ability check with the DC equal to 10+(the level of the spell they are trying to counter). A seventh level spell has a DC to counter of 17. A 9th level spell has a DC to counter of 19 and a 5th level spell has a DC to counter of 15 if they are not automatically countered by using a counterspell of a level equal to or greater than the level of the spell you are trying to counter.
Example:
Player A casts a 7th level spell at player B
Player B casts counterspell using a 5th level slot (since they didn't know what level the spell cast at them was). They have to make a spellcasting ability check which is a d20+spellcasting modifier and must roll greater than or equal to the DC which is 10+(the level of the spell you are trying to counter) which is 17 in this case.
Player B has 20 int, and rolls a 12 ... 12+5 = 17 which succeeds in counterspelling the 7th level spell.
Player A decides to counterspell player B. They could use a 5th level slot to cast counterspell and automatically succeed. However, let's say they only have a 3rd level slot left. They cast counterspell using a third level slot. Since this is less than the 5th level slot used by player B it does not automatically counter their spell. The DC is 10+(the level of the spell they want to counter). In this case, Player B's counterspell was cast using a 5th level slot and the DC is thus 15. Player A has to roll greater than 15 on a d20+spellcasting modifier in order to succeed on the ability check and counter player B's counterspell. If player A has int 18 +4) and rolls a 13 the total is 17 and player A succeeds in countering the counterspell and their original 7th level spell goes off.
Both player A and B have used their reactions for the round. This means that they can not cast additional counterspells or shield or take op attacks or do anything that needs a reaction until their next turn. Any other casters however could still use their reactions to cast counterspell if they have both the reaction available and the spell.
The issue in contention is people think that upcasting has no added value -- or change in outcome. People are saying that it's simply pass or fail, however, the 3rd sentence explicitly states an ability check must be made for 4th or higher for when "it" the spell isn't automatically, countered. WHAT IS THAT FORMULA?
Let me try to explain. The developers are bad at wording.
The DC is always 10+target spell level for spells over 4th level (regardless of counterspell level).
The way it is worded if the target spell is level 4 and you counter using a level 4 slot, you make a DC 14 ability check, if you succeed the spell is countered, but the spell is countered regardless because you used a 4th level slot.
Rather than say you make an ability check if the target spell is 4th level or higher, they should have said to make an ability check if the target spell is higher than counterspell's level. But the result is the same regardless. Even if the check is required by RAW, the result can be and is superseded by the higher level effect of the spell.
Final examples:
Target casts a level 9 spell, you counter with a level 3 slot. DC19 spellcasting ability check to counter.
Target casts a level 9 spell, you counter with a level 8 slot. DC19 spellcasting ability check to counter.
Target casts a level 9 spell, you counter with a level 9 slot. Spell is countered regardless of check.
If you are still confused why anyone would upcast counterspell, remember that the DM does not have to tell you the spell or level that is being cast.
What if I’m casting a 5th level spell but I need to sacrifice a 7th level spell slot to cast it. This spell doesn’t benefit from upcasting in this example. Does the counter spell need to be at 5th or 7th to automatically succeed?
What if I’m casting a 5th level spell but I need to sacrifice a 7th level spell slot to cast it. This spell doesn’t benefit from upcasting in this example. Does the counter spell need to be at 5th or 7th to automatically succeed?
It doesn't matter if the spell benefits from being upcast, it's still been upcast, so counterspell treats it as a 7th level spell.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
Use passive Arcana scores then. 20 Intelligence (+5), level 8 Wizard (+3 Prof Bonus) and proficiency in Arcana has a Passive Arcana of 18 and can recognize spells of up to 3rd level automatically without using a reaction. That’s probably the easiest way to rule it.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
It is likely to take a while for a wizard to get 20 intellignce and expertise in arcane (the later only being available as a multiclass or a feat which will be competeing with ASIs, warcaster and the likes, but I will let that slide.
I have no real word experience to tell how difficult it is for an intelligent practicioner of the arcane arts to identify what spell is being cast my another spellcaster and at what level so I have to go by the rules.
XGTE says that identifying a spell as it is being cast uses a reaction and while a wizard with int 20 and expertise in arcana might find nearly always succeed in identifting when the another spellcast casts firebolt (DC15 with advantage) there will be considerable chance of failure to identify when an enemy cleric is casting mass heal (DC24). It does not give an indication whether the spell level is known though it might be reasonable ot say that is only the case if you exceed the DC by 5.
So on the face of it if you spend as the other spellcaster starts casting you only have time ot immediately try to counter it without knowing what the spell is as you do not have two reactions, though a sage advice muddied the waters by saying one character can use their reaction to identify the spell and then tell his friend what it is who would still have time to counter it but I, find that advise odd as if I need ot respond to a spell so quickly that I can't identify it first how come my friend has time ot identify it, then tell me what itis and I still have time to counterspell it?
In practise at the table if the DM says the bad guy casts a spell and one of the players says "can I identify it" and then roll an arcana check and then tell his friend what it is and then his friend decides to counterspell it it all takes far too long. To expediate gameplay players and DMs usually announce the spell they are casting but not the level leaving the player to decide if and how to counter it. If you know (and your character) know the base level of the spell is 7, there is no pont casting counterspell at level 4-6 (unless you are out of level 3 slots), level 7 means you will succeed unless it was upcast and level 9 means you will always succeeed.
Counterspell is a very powerful spell to the point that having it always succeed can be detrimental to the game having the PCs have to gamble on what level to cast counterspell at restores some of the balance.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
Use passive Arcana scores then. 20 Intelligence (+5), level 8 Wizard (+3 Prof Bonus) and proficiency in Arcana has a Passive Arcana of 18 and can recognize spells of up to 3rd level automatically without using a reaction. That’s probably the easiest way to rule it.
The proficiency bonus is not added to the ability check unless a particular features adds it, such as an abjuration wizard or a bard's jack of all trades.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
Use passive Arcana scores then. 20 Intelligence (+5), level 8 Wizard (+3 Prof Bonus) and proficiency in Arcana has a Passive Arcana of 18 and can recognize spells of up to 3rd level automatically without using a reaction. That’s probably the easiest way to rule it.
The proficiency bonus is not added to the ability check unless a particular features adds it, such as an abjuration wizard or a bard's jack of all trades.
I’m speaking about Identifying spells, not Countering them. Identifying spells uses Arcana checks and I’m saying you can rule that passive Arcana is good enough to identify a spell without using a reaction (in contrast to the sourcebooks that say to identify a spell being cast you have to use your reaction and an Arcana check).
Edit: ideally, with this process you can more accurately tell what spell is being cast and therefore decide on the level of Counterspell needed to deflect it without a Counterspell ability check.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) . without doing so you are opening yourself up for heavy metagaming and undermining player choice. No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell. If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff. It costs a higher level spell, it isn't like it is free. Additionally the risk reward is way worse the higher level you cast and missing it by one level.
Use passive Arcana scores then. 20 Intelligence (+5), level 8 Wizard (+3 Prof Bonus) and proficiency in Arcana has a Passive Arcana of 18 and can recognize spells of up to 3rd level automatically without using a reaction. That’s probably the easiest way to rule it.
The proficiency bonus is not added to the ability check unless a particular features adds it, such as an abjuration wizard or a bard's jack of all trades.
I’m speaking about Identifying spells, not Countering them. Identifying spells uses Arcana checks and I’m saying you can rule that passive Arcana is good enough to identify a spell without using a reaction (in contrast to the sourcebooks that say to identify a spell being cast you have to use your reaction and an Arcana check).
Edit: ideally, with this process you can more accurately tell what spell is being cast and therefore decide on the level of Counterspell needed to deflect it without a Counterspell ability check.
This all sounds like homebrew. Again, nothing wrong with homebrew. But this is a thread about the actual counterspell mechanics in question, not about how to homebrew them into working differently.
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I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
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If it is not automatically countered -- How do you perform the ability check. What is the calculation? What is the formula? DC='s 10+ ???
There is no confusion as to what "it" is... I used several examples to properly iterate and illustrate the proper understanding of the word "it." The issue in contention is people think that upcasting has no added value -- or change in outcome. People are saying that it's simply pass or fail, however, the 3rd sentence explicitly states an ability check must be made for 4th or higher for when "it" the spell isn't automatically, countered. WHAT IS THAT FORMULA?
The forumla for the DC remains the same: 10 + the level of the spell you're trying to counter.
Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond.
Need help with Homebrew? Check out ✨ this FAQ/Guide thread ✨ by IamSposta.
What is the calculation? Well here is the formula that you can plug into Excel/Sheets/Openoffice:
IF (counterspell_spell_slot_level, >= target_spell_slot_level, DC=0,DC=10+target_spell_slot_level)
Make Column A counterspell_spell_slot_level. Make column B target_spell_slot_level. Make column C DC. Make column D ability_modifier. Make column E minimum roll needed. Since on ability checks 1's do not automatically fail, a DC of 0 represents automatic success. The DC formula would then look like the following: =IF(A2>=B2,0,10+B2) and the minimum roll needed would be =IF(C2-D2>0,C2-D2,1)
Hope that helps with your visualization.
The base casting of the spell calls for a skill check specifically at 4th level, because it's a 3rd a level spell by default. But the required spell level trigger for requiring a skill check is changed based on the text found in casting at higher levels.
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@OP: There are 5 people trying to tell you that you are over complicating the interpretation of this spell.
You attempt to interrupt a creature in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect (Because the lowest level Counterspell can be cast is level 3. Therefore the Counterspell you cast is equal to or greater than the spell being cast by the other creature). If it (the creature) is casting a spell of 4th level or higher, make an ability check using your spellcasting ability (ie: when you're casting it at level 3). The DC equals 10 + the spell's level (of the spell being cast by the creature). On a success (if you succeed the check), the creature's spell fails and has no effect.
At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the interrupted spell has no effect if its level (its level = the interrupted spell) is less than or equal to the level of the spell slot you used. (ie: if the creature casts a level 4 spell, and you cast a level 4 or greater counterspell, no check is required. If the creature casts a level 7 spell and you cast a level 7 or greater counterspell, no check is required. Etc...)
As mentioned ...
1) The DC for the ability check IS 10+ (the level of the spell you are trying to counter)
2) You only need to make an ability check IF the spell slot level you used for counterspell is less than the level of the spell you are trying to counter. If you use a spell slot for counterspell that is equal to or greater than the level of the spell you are trying to counter then you automatically succeed.
If the DC is required it is always 10+ (the level of the spell you are trying to counter)
If someone uses a 5th level slot to cast a fireball, the DC, IF required will be 15. The DC is ONLY required if you cast counterspell with a 4th level or lower slot.
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You may ask why this matters .. in many games when someone (either the NPCs or the players have counterspell), all the player or DM says is that they are casting a spell since that is typically all that is known at the time the spell is cast. Neither players nor NPCs know what spell is being cast or what spell level it is being cast at. As a result, the player (or NPC) has to consider or guess what level of spell slot to use for counterspell since to automatically counter the spell they need to use a slot equal to or greater than the spell being cast.
If they fail to choose the correct level for the counterspell or they don't have a high enough level spell slot then they have to make an ability check with the DC equal to 10+(the level of the spell they are trying to counter). A seventh level spell has a DC to counter of 17. A 9th level spell has a DC to counter of 19 and a 5th level spell has a DC to counter of 15 if they are not automatically countered by using a counterspell of a level equal to or greater than the level of the spell you are trying to counter.
Example:
Player A casts a 7th level spell at player B
Player B casts counterspell using a 5th level slot (since they didn't know what level the spell cast at them was). They have to make a spellcasting ability check which is a d20+spellcasting modifier and must roll greater than or equal to the DC which is 10+(the level of the spell you are trying to counter) which is 17 in this case.
Player B has 20 int, and rolls a 12 ... 12+5 = 17 which succeeds in counterspelling the 7th level spell.
Player A decides to counterspell player B. They could use a 5th level slot to cast counterspell and automatically succeed. However, let's say they only have a 3rd level slot left. They cast counterspell using a third level slot. Since this is less than the 5th level slot used by player B it does not automatically counter their spell. The DC is 10+(the level of the spell they want to counter). In this case, Player B's counterspell was cast using a 5th level slot and the DC is thus 15. Player A has to roll greater than 15 on a d20+spellcasting modifier in order to succeed on the ability check and counter player B's counterspell. If player A has int 18 +4) and rolls a 13 the total is 17 and player A succeeds in countering the counterspell and their original 7th level spell goes off.
Both player A and B have used their reactions for the round. This means that they can not cast additional counterspells or shield or take op attacks or do anything that needs a reaction until their next turn. Any other casters however could still use their reactions to cast counterspell if they have both the reaction available and the spell.
Let me try to explain. The developers are bad at wording.
The DC is always 10+target spell level for spells over 4th level (regardless of counterspell level).
The way it is worded if the target spell is level 4 and you counter using a level 4 slot, you make a DC 14 ability check, if you succeed the spell is countered, but the spell is countered regardless because you used a 4th level slot.
Rather than say you make an ability check if the target spell is 4th level or higher, they should have said to make an ability check if the target spell is higher than counterspell's level. But the result is the same regardless. Even if the check is required by RAW, the result can be and is superseded by the higher level effect of the spell.
Final examples:
If you are still confused why anyone would upcast counterspell, remember that the DM does not have to tell you the spell or level that is being cast.
Yet another reason why Abjuration Wizards are awesome, add proficiency bonus to the roll as well.
What if I’m casting a 5th level spell but I need to sacrifice a 7th level spell slot to cast it. This spell doesn’t benefit from upcasting in this example. Does the counter spell need to be at 5th or 7th to automatically succeed?
It doesn't matter if the spell benefits from being upcast, it's still been upcast, so counterspell treats it as a 7th level spell.
As a DM I would adjust the DC if it is cast at higher levels reducing the DC by -1 to their check for each level above 3.
So a 6th level vs level 3 counter spell is DC 16
And a 6th level vs level 4 counter spell is a DC 15
You are using more magic to unweave their magic so your spell should get a little help. If you fell that is too strong and feel there should be a pay out, then you can use the spiritual weapon/shadow blade where two levels is needed to increase potency. (So a level 6 spell vs level 5 counter spell is a DC 15).
There is nothing wrong with doing so, but do know it is a homebrew rule change, and, by default that isn't how the spell works.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
IMO, it is a mistake that Counter spell and Dispel Magic doesn't have this and is in fact a typo (as there are a LOT of spells with partial explanations) .
without doing so you are opening yourself up for heavy metagaming and undermining player choice.
No freaking way a wizard with 20 in intelligence and expertise in Arcana is going to not have an idea how strong he needs his counterspell.
If you are a GM war gamer? I am going to be pressed to metagame the spells to not wiff.
It costs a higher level spell, it isn't like it is free.
Additionally the risk reward is way worse the higher level you cast and missing it by one level.
Use passive Arcana scores then. 20 Intelligence (+5), level 8 Wizard (+3 Prof Bonus) and proficiency in Arcana has a Passive Arcana of 18 and can recognize spells of up to 3rd level automatically without using a reaction. That’s probably the easiest way to rule it.
It is likely to take a while for a wizard to get 20 intellignce and expertise in arcane (the later only being available as a multiclass or a feat which will be competeing with ASIs, warcaster and the likes, but I will let that slide.
I have no real word experience to tell how difficult it is for an intelligent practicioner of the arcane arts to identify what spell is being cast my another spellcaster and at what level so I have to go by the rules.
XGTE says that identifying a spell as it is being cast uses a reaction and while a wizard with int 20 and expertise in arcana might find nearly always succeed in identifting when the another spellcast casts firebolt (DC15 with advantage) there will be considerable chance of failure to identify when an enemy cleric is casting mass heal (DC24). It does not give an indication whether the spell level is known though it might be reasonable ot say that is only the case if you exceed the DC by 5.
So on the face of it if you spend as the other spellcaster starts casting you only have time ot immediately try to counter it without knowing what the spell is as you do not have two reactions, though a sage advice muddied the waters by saying one character can use their reaction to identify the spell and then tell his friend what it is who would still have time to counter it but I, find that advise odd as if I need ot respond to a spell so quickly that I can't identify it first how come my friend has time ot identify it, then tell me what itis and I still have time to counterspell it?
In practise at the table if the DM says the bad guy casts a spell and one of the players says "can I identify it" and then roll an arcana check and then tell his friend what it is and then his friend decides to counterspell it it all takes far too long. To expediate gameplay players and DMs usually announce the spell they are casting but not the level leaving the player to decide if and how to counter it. If you know (and your character) know the base level of the spell is 7, there is no pont casting counterspell at level 4-6 (unless you are out of level 3 slots), level 7 means you will succeed unless it was upcast and level 9 means you will always succeeed.
Counterspell is a very powerful spell to the point that having it always succeed can be detrimental to the game having the PCs have to gamble on what level to cast counterspell at restores some of the balance.
The proficiency bonus is not added to the ability check unless a particular features adds it, such as an abjuration wizard or a bard's jack of all trades.
"Not all those who wander are lost"
I’m speaking about Identifying spells, not Countering them. Identifying spells uses Arcana checks and I’m saying you can rule that passive Arcana is good enough to identify a spell without using a reaction (in contrast to the sourcebooks that say to identify a spell being cast you have to use your reaction and an Arcana check).
Edit: ideally, with this process you can more accurately tell what spell is being cast and therefore decide on the level of Counterspell needed to deflect it without a Counterspell ability check.
This all sounds like homebrew. Again, nothing wrong with homebrew. But this is a thread about the actual counterspell mechanics in question, not about how to homebrew them into working differently.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.