Hello all! First post, so pardon any rules issues. I'll try my best :)
So, I've been plotting a EK/Bladesinger mix, and I've become rather fond of wielding a rapier in one hand and an arcane focus (staff) in the other, a la Gandalf. Of course, I would like to take the dueling fighting style, to snag that damage boost.
So here is the issue; duelist cannot be used when you have a weapon in both hands, and I already know that a staff can be used as a quarterstaff. My question is, is an arcane focus automatically regarded as a weapon? Or is its use as a quarterstaff purely as an improvised weapon, and therefore is compatible with duelist style?
According to the rules on magic items, magic staves "can be used as a quarterstaff", unless otherwise indicated. The interesting thing is that this is specifically in the magic items section, but a regular arcane focus isn't a magic item, so your DM may choose to allow it or not for non-magical staves. Along the same lines, it doesn't say "also counts as a quarterstaff," but rather "can be used as a quarterstaff." So again, some ambiguity.
As a DM, this is where I might be flexible and let the player decide: you get to choose, and it always behaves one way or the other. Either the staff is a focus only and you cannot make melee attacks with it (like a wand or an orb) or it is a weapon and you lose the benefits of the fighting style.
Edit: DDB seems to only allow you to wield a magical staff as a quarter staff, which is the strict RAW interpretation. So according to that interpretation, a non-magical staff is not a weapon and essentially indistinguishable from the other focii.
Using D&D Beyoncé’s (that’s an autocorrect but I’m leaving it in) set-up as an indication of rules is always a bad idea. The Revenant Double-bladed Scimitar isn’t an item at ALL, for example.
To OP’s question: yes, a staff is a weapon. A staff is always a weapon. I’d be happy to work something out if one of my players wanted to do something like this, but it’d be a houserule thing. By RAW, you can’t benefit from duelist with a staff in your off-hand. You could use a wand instead if your DM is obsessed with RAW, but most DMs should be flexible enough to work something out with you.
By the actual words on the page RAW, that is incorrect. The words on the page make a distinction between a staff and a quarterstaff and give rules to each of them, with a further set for magical staves (that don't necessarily apply to non-magic staves and can be interpreted to be in line with the improvised weapon rules rather than a rule making that category of magic items weapons). Your interpretation may be RAI or rules as you think they are, but I mentioned the relevant text on the page and possible interpretations, then pointed out what DDB does.
By the actual words on the page RAW, that is incorrect. The words on the page make a distinction between a staff and a quarterstaff and give rules to each of them, with a further set for magical staves (that don't necessarily apply to non-magic staves). Your interpretation may be RAI or rules as you think they are, but I mentioned the relevant text on the page and possible interpretations, then pointed out what DDB does.
The actual words on the page say that a staff focus is a staff. 5e relies on common sense a lot to establish what RAW is, much to the chagrin of... actually quite a lot of people. You have to deliberately ignore what words mean to justify your position that a staff focus is just a focus and not a staff. But honestly it's fair if that's not satisfactory to you.
I actually don't disagree with you and would treat a staff as a quarterstaff, but I think that it is a ruling to make those two distinct things in the game overlap. I also think that if a wizard could wield a wand and a sword and benefit from the fighting style, then I think there is no harm in letting him use his staff instead, as long as he never tries to make melee attacks with it and it confers to him no benefits that he wouldn't get from the wand.
Edit: But, with all that being said, Gandalf certainly does swing both at his foes in the movies, so maybe dueling isn't the best fighting style to simulate his movie portrayal.
Edit 2: Note that quarterstaves are a subset of staves in idiomatic English, and quarterstaves are the ones that are listed as being weapons.
It is possible to hold a weapon and not be wielding it as such. A two-handed weapon is impossible to wield with one hand, but one hand can hold a bow while the other holds a rapier.
There could be some debate weather an object that functions as both a focus and weapon can be used as one while not counting as the other, but I would work with the player to accomplish their idea. If they don't get rules tricky on me, I won't get rules tricky on them.
My question is, is an arcane focus automatically regarded as a weapon? Or is its use as a quarterstaff purely as an improvised weapon, and therefore is compatible with duelist style?
First point, an arcane focus staff is not a quarterstaff (a stout wooden pole tipped with iron). If you hit someone with your arcane focus, it is similar enough to a quarterstaff that under the improvised weapon rules you can treat it as a quarterstaff. As an aside, do you really want to be hitting people with your 5GP arcane focus?
With the Dueling fighting style, you have to be holding "no other weapons". In other plces in the rulebook, the term "weapon" means "something on the weapons table" not "something you can hit foes with", so I think for the Dueling style the same applies. As long as whatever is in your other hand is not an actual weapon on the weapon table, you are fine.
On the other hand, I think you could say that the spirit of the style is that you don't hold anything potentially dangerous in the other hand, so a GM might disallow improvised weapons along with anything that could be dangerous (bricks, frying pans). I think the sprit of the rule is that your other hand is only for balance, dramtic gestures, swinging from chandeliers, and grabbing damsels in distress. :-)
My flute is my spellcasting focus. It is still a flute.
It seems to me we are chasing two questions.
I believe the real question is "May I use the benefits of the dualist style if I have my arcane focus staff in my off-hand?"
The second question that folks appear to wish to discuss is "Is an arcane focus a weapon (quarterstaff)?"
To the first question, I say Ask your DM.
To the second question, it seems the rules state you may attack with an arcane focus staff in the same manner that you would attack with a quarterstaff. Therefore, as I suggested in my first sentence, the staff appears to be a quarterstaff that is also capable of serving as an arcane focus. If this is the case, does using your arcane focus appear to be an end-run around the rules as intended? Or, is this like my position on two weapon fighting, where I think it should be OK to fight with rapier and dagger without doing anything like selecting a feat. Everyone is entitled to their opinion, but on game night, the DM's opinion is the only one that matters.
P.S. Let's not hijack this thread and talk about two-weapon fighting.
No.The real question is second one. The answer to the first is that you can use the duelist feat with an orb or wand because they are not weapons. This is not in question.
And as I said in the first reply the answer to the second question (is a focus staff a quarterstaff?) requires interpretation. Does the sentence "Unless a staff’s description says otherwise, a staff can be used as a quarterstaff." unambiguously make all magic staves quarterstaves (weapons) or just allow them to be treated under the improvised weapons rule as quarterstaves? Beyond that, does this sentence that describes magic items apply to mundane focii? Those are both points of DM interpretation because they are not obvious by the text on the page.
I would say under strict RAW, the sentence that describes magic items doesn't apply to mundane focii, even though the text of those category descriptions are general and don't describe anything inherently special about magical nature of magic items of those kinds.
This is a "nobody is completely correct, and nobody is completely incorrect" type of situation. The only thing that is 100% firm by RAW is that magic item staves can be considered weapons, yet they do not have to be considered weapons. That's a position that I'm not seeing anyone disagree with, but it's not satisfactory for anyone either. I think the devs purposely left this ambiguity in place for DMs & players to decide on a campaign-by-campaign, case-by-case (magic vs mundane), or even item-by-item basis.
The only thing I have a strong opinion on (which is, frankly, odd for me) is that whatever you choose in your game should be definitive.
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You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
I concur with Sigred; it seems the argument is going in circles at this point. The major takeaways I've seen are:
-the rules on whether or not a staff (focus) is also a quarterstaff are ambiguous at best (probably on purpose)
-If a decision is made, it must remain consistent throughout the campaign, which could cause some rather sticky situations in the future, since there are magic staves that can be used as both foci and melee weapons (the staff of power and the staff of the magi, to name two).
ALTHOUGH, when re-reading the descriptions for the staves of power and magi, they rather explicitly state that the can be used as magic quarterstaves, a bit of text that is absent from most other magic staves. Do we think this has any significance?
Sigred's got the right of it, methinks. This is a case where the RAW is ambiguous, probably deliberately so, and while that vexes the hell out of a subset of players, it's there for a reason.
If a player at my table wanted to benefit from Dueling with a rapier while holding their staff in the off hand, I'd probably let them. +2 damage is good but not fantabulo-amazeballs, Gandalfing is cool, and holding the stick means they're not holding anything else that might be more useful. This wouldn't even be a question with any other type of focus; why screw with somebody's desired flavor if they're not likely to dickbat you on the rules? RAW, the player can't two-weapon fight with the stick and the sword anyways unless they take the crappy feat.
If the player started making a habit of clonking people with the stick, or if they took the crappy feat with the intent of stick-clonking, I'd simply rule that their fighting style has changed to Two-Weapon Fighting due to a shift in their focus/emphasis. If they wanted to argue the point, that's what DM Pants are for. Put them on and inform the player that abuse of DM largesse results in DM largesse being revoked.
From a RAW perspective, I don't see the dual item/weapon nature of a staff/quarterstaff as any more troublesome than holding a shield which has the loaded possibility of becoming an improvised weapon at the drop of a hat. From a RAF/RAI perspective, if the player is signaling that they're planning on doing the Dueling/TWF grasp dance exploit that has been talked about in other threads, then sure, maybe tell them a Stave is always a weapon and nip it in the bud... but if the player is really only trying to hold their arcane focus in their offhand and wants to use a stave instead of a rod, there's absolutely no reason to be punishing them for their choice of flavor.
A note about the magic items that I could easily read: the general trend seems to be that ones with a + to attack and damage rolls tend to say that they can be wielded as a quarterstaff as part of the text describing that bonus, whereas the ones without a bonus to hit do not have the text saying that they can be used as a quarterstaff.
ALTHOUGH, when re-reading the descriptions for the staves of power and magi, they rather explicitly state that the can be used as magic quarterstaves, a bit of text that is absent from most other magic staves. Do we think this has any significance?
A note about the magic items that I could easily read: the general trend seems to be that ones with a + to attack and damage rolls tend to say that they can be wielded as a quarterstaff as part of the text describing that bonus, whereas the ones without a bonus to hit do not have the text saying that they can be used as a quarterstaff.
I was going to say what Wolf said. Only the staffs that are treated as +X magic weapons have the extra mention in their description. The general rule that staffs can be used as quarterstaffs still applies to the others regardless.
Whether a +1 Spell Focus (Staff) can necessarily be used as a +1 Quarterstaff for weapon attacks isn't answered, possibly simply because a +1 Spell Focus (staff or otherwise) isn't actually a thing that exists in general (though, specific named staffs or foci like the Staff of Power may include +'s that are explicitly limited to weapon attacks). For a DM navigating that question in a situation where they've handed out a +1 Spell Focus (Staff), for parity's sake, I would humbly suggest that they treat it the same as they would for a Warlock with Improved Pact Weapon using a +1 Quarterstaff as a spell focus... which, based on the description of Weapon, +1 applying to attack and damage rolls "made with" the item, I think clearly would apply to spell attacks and damage using it as a focus.
Room for disagreement there, but it's the simplest reading of +1 Weapon, and agree or disagree about the intent it's equally supported by the text, and I don't see any reason to treat a magical enhancement as more effective going weapon -> focus than a similar enhancement going focus -> weapon.
Thinking about this one, I'm not sure where to draw the line.
Would you allow duelling style to work if the character was holding a sword in the second hand, ? Probably not. How about spellcasting focus orb or a component pouch? Probably yes. How about a frying pan? A brick? A rolled up cloak? A gnome?
Sometimes I'm baffled by how far people will try to look at ultra specific wording to affect rulings in a game where the DM literally just makes everything up on the fly. You don't gain benefit from Duellist if you are holding another weapon in your other weapon. A staff is a weapon, whether you call it a quarter staff or a staff. Bear in mind when applying your thinking that under the Monk class, you're specifically allowed to rename weapons to whatever you want and they are still weapons. If your monk calls his offhand weapon a Moon Pie that doesn't change the fact that it's actually a dagger. The game rules are designed around people applying good sense to them (because DnD is a game of infinite possibilities) and not rules lawyers.
If you are holding a staff in your second hand, you are holding a weapon in that hand. It's clearly a weapon. You know it's a weapon, because if you were disarmed of your sword, you would wield the staff. You even reference Gandalf in the LOTR movies, who we see whacking orcs with it... as a weapon. If you hit someone with it, everyone would say "They hit that guy with a weapon," not "they hit that gut with a six foot long wooden arcane focus." If you made your arcane focus a "four foot long metal blade" then it's a sword even if you are calling it by a different name.
Use common sense for these things. The rules are there to help you tell magnificent stories.
Can you fight with a sword in one hand and a staff in the other? Sure. Can you gain Duellist bonus? No. You're very specifically breaking the one condition that prevents you gaining Duellist bonus.
To make this work for you in your campaign: agree with your DM that your arcane focus is not considered a quarterstaff because it's too light, and if ever it's used in combat it will count as an Improvised Weapon (termed in the PHB as "anything that doesn't resemble a weapon that can be wielded in one or two hands."). Technically the arcane focus staff does resemble a weapon, but by being too light, it can be counted like any other object as improvised. If ever you use it in combat it would therefore count as Improvised and therefore deals only 1d4 damage. Duellist says you cannot have a Weapon in your other hand... but anything in the world that you can pick up can be used as an improvised weapon. Clearly you can be a Duellist with a sword in one hand and a bottle or bunch of flowers in the other (you can even have a shield). You still won't be able to make bonus action two-weapon-fighting attacks with it in any case, as it's not a Light Weapon anyway.
Duelist only requires you to be wielding only 1 weapon, it doesn't restrict you from benefiting from it while holding a weapon you are not using in your other hand. I said as much 4 days ago.
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Hello all! First post, so pardon any rules issues. I'll try my best :)
So, I've been plotting a EK/Bladesinger mix, and I've become rather fond of wielding a rapier in one hand and an arcane focus (staff) in the other, a la Gandalf. Of course, I would like to take the dueling fighting style, to snag that damage boost.
So here is the issue; duelist cannot be used when you have a weapon in both hands, and I already know that a staff can be used as a quarterstaff. My question is, is an arcane focus automatically regarded as a weapon? Or is its use as a quarterstaff purely as an improvised weapon, and therefore is compatible with duelist style?
Thank you for your time!
According to the rules on magic items, magic staves "can be used as a quarterstaff", unless otherwise indicated. The interesting thing is that this is specifically in the magic items section, but a regular arcane focus isn't a magic item, so your DM may choose to allow it or not for non-magical staves. Along the same lines, it doesn't say "also counts as a quarterstaff," but rather "can be used as a quarterstaff." So again, some ambiguity.
As a DM, this is where I might be flexible and let the player decide: you get to choose, and it always behaves one way or the other. Either the staff is a focus only and you cannot make melee attacks with it (like a wand or an orb) or it is a weapon and you lose the benefits of the fighting style.
Edit: DDB seems to only allow you to wield a magical staff as a quarter staff, which is the strict RAW interpretation. So according to that interpretation, a non-magical staff is not a weapon and essentially indistinguishable from the other focii.
Using D&D Beyoncé’s (that’s an autocorrect but I’m leaving it in) set-up as an indication of rules is always a bad idea. The Revenant Double-bladed Scimitar isn’t an item at ALL, for example.
To OP’s question: yes, a staff is a weapon. A staff is always a weapon. I’d be happy to work something out if one of my players wanted to do something like this, but it’d be a houserule thing. By RAW, you can’t benefit from duelist with a staff in your off-hand. You could use a wand instead if your DM is obsessed with RAW, but most DMs should be flexible enough to work something out with you.
By the actual words on the page RAW, that is incorrect. The words on the page make a distinction between a staff and a quarterstaff and give rules to each of them, with a further set for magical staves (that don't necessarily apply to non-magic staves and can be interpreted to be in line with the improvised weapon rules rather than a rule making that category of magic items weapons). Your interpretation may be RAI or rules as you think they are, but I mentioned the relevant text on the page and possible interpretations, then pointed out what DDB does.
The actual words on the page say that a staff focus is a staff. 5e relies on common sense a lot to establish what RAW is, much to the chagrin of... actually quite a lot of people. You have to deliberately ignore what words mean to justify your position that a staff focus is just a focus and not a staff. But honestly it's fair if that's not satisfactory to you.
I actually don't disagree with you and would treat a staff as a quarterstaff, but I think that it is a ruling to make those two distinct things in the game overlap. I also think that if a wizard could wield a wand and a sword and benefit from the fighting style, then I think there is no harm in letting him use his staff instead, as long as he never tries to make melee attacks with it and it confers to him no benefits that he wouldn't get from the wand.
Edit: But, with all that being said, Gandalf certainly does swing both at his foes in the movies, so maybe dueling isn't the best fighting style to simulate his movie portrayal.
Edit 2: Note that quarterstaves are a subset of staves in idiomatic English, and quarterstaves are the ones that are listed as being weapons.
It is possible to hold a weapon and not be wielding it as such. A two-handed weapon is impossible to wield with one hand, but one hand can hold a bow while the other holds a rapier.
There could be some debate weather an object that functions as both a focus and weapon can be used as one while not counting as the other, but I would work with the player to accomplish their idea. If they don't get rules tricky on me, I won't get rules tricky on them.
First point, an arcane focus staff is not a quarterstaff (a stout wooden pole tipped with iron). If you hit someone with your arcane focus, it is similar enough to a quarterstaff that under the improvised weapon rules you can treat it as a quarterstaff. As an aside, do you really want to be hitting people with your 5GP arcane focus?
With the Dueling fighting style, you have to be holding "no other weapons". In other plces in the rulebook, the term "weapon" means "something on the weapons table" not "something you can hit foes with", so I think for the Dueling style the same applies. As long as whatever is in your other hand is not an actual weapon on the weapon table, you are fine.
On the other hand, I think you could say that the spirit of the style is that you don't hold anything potentially dangerous in the other hand, so a GM might disallow improvised weapons along with anything that could be dangerous (bricks, frying pans). I think the sprit of the rule is that your other hand is only for balance, dramtic gestures, swinging from chandeliers, and grabbing damsels in distress. :-)
My flute is my spellcasting focus. It is still a flute.
It seems to me we are chasing two questions.
I believe the real question is "May I use the benefits of the dualist style if I have my arcane focus staff in my off-hand?"
The second question that folks appear to wish to discuss is "Is an arcane focus a weapon (quarterstaff)?"
To the first question, I say Ask your DM.
To the second question, it seems the rules state you may attack with an arcane focus staff in the same manner that you would attack with a quarterstaff. Therefore, as I suggested in my first sentence, the staff appears to be a quarterstaff that is also capable of serving as an arcane focus. If this is the case, does using your arcane focus appear to be an end-run around the rules as intended? Or, is this like my position on two weapon fighting, where I think it should be OK to fight with rapier and dagger without doing anything like selecting a feat. Everyone is entitled to their opinion, but on game night, the DM's opinion is the only one that matters.
P.S. Let's not hijack this thread and talk about two-weapon fighting.
Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt
No.The real question is second one. The answer to the first is that you can use the duelist feat with an orb or wand because they are not weapons. This is not in question.
And as I said in the first reply the answer to the second question (is a focus staff a quarterstaff?) requires interpretation. Does the sentence "Unless a staff’s description says otherwise, a staff can be used as a quarterstaff." unambiguously make all magic staves quarterstaves (weapons) or just allow them to be treated under the improvised weapons rule as quarterstaves? Beyond that, does this sentence that describes magic items apply to mundane focii? Those are both points of DM interpretation because they are not obvious by the text on the page.
I would say under strict RAW, the sentence that describes magic items doesn't apply to mundane focii, even though the text of those category descriptions are general and don't describe anything inherently special about magical nature of magic items of those kinds.
This is a "nobody is completely correct, and nobody is completely incorrect" type of situation. The only thing that is 100% firm by RAW is that magic item staves can be considered weapons, yet they do not have to be considered weapons. That's a position that I'm not seeing anyone disagree with, but it's not satisfactory for anyone either. I think the devs purposely left this ambiguity in place for DMs & players to decide on a campaign-by-campaign, case-by-case (magic vs mundane), or even item-by-item basis.
The only thing I have a strong opinion on (which is, frankly, odd for me) is that whatever you choose in your game should be definitive.
You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
Holy cow, so many replies! Thank you, everyone!
I concur with Sigred; it seems the argument is going in circles at this point. The major takeaways I've seen are:
-the rules on whether or not a staff (focus) is also a quarterstaff are ambiguous at best (probably on purpose)
-If a decision is made, it must remain consistent throughout the campaign, which could cause some rather sticky situations in the future, since there are magic staves that can be used as both foci and melee weapons (the staff of power and the staff of the magi, to name two).
ALTHOUGH, when re-reading the descriptions for the staves of power and magi, they rather explicitly state that the can be used as magic quarterstaves, a bit of text that is absent from most other magic staves. Do we think this has any significance?
Sigred's got the right of it, methinks. This is a case where the RAW is ambiguous, probably deliberately so, and while that vexes the hell out of a subset of players, it's there for a reason.
If a player at my table wanted to benefit from Dueling with a rapier while holding their staff in the off hand, I'd probably let them. +2 damage is good but not fantabulo-amazeballs, Gandalfing is cool, and holding the stick means they're not holding anything else that might be more useful. This wouldn't even be a question with any other type of focus; why screw with somebody's desired flavor if they're not likely to dickbat you on the rules? RAW, the player can't two-weapon fight with the stick and the sword anyways unless they take the crappy feat.
If the player started making a habit of clonking people with the stick, or if they took the crappy feat with the intent of stick-clonking, I'd simply rule that their fighting style has changed to Two-Weapon Fighting due to a shift in their focus/emphasis. If they wanted to argue the point, that's what DM Pants are for. Put them on and inform the player that abuse of DM largesse results in DM largesse being revoked.
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From a RAW perspective, I don't see the dual item/weapon nature of a staff/quarterstaff as any more troublesome than holding a shield which has the loaded possibility of becoming an improvised weapon at the drop of a hat. From a RAF/RAI perspective, if the player is signaling that they're planning on doing the Dueling/TWF grasp dance exploit that has been talked about in other threads, then sure, maybe tell them a Stave is always a weapon and nip it in the bud... but if the player is really only trying to hold their arcane focus in their offhand and wants to use a stave instead of a rod, there's absolutely no reason to be punishing them for their choice of flavor.
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I'm going to make this way harder than it needs to be.
A note about the magic items that I could easily read: the general trend seems to be that ones with a + to attack and damage rolls tend to say that they can be wielded as a quarterstaff as part of the text describing that bonus, whereas the ones without a bonus to hit do not have the text saying that they can be used as a quarterstaff.
I was going to say what Wolf said. Only the staffs that are treated as +X magic weapons have the extra mention in their description. The general rule that staffs can be used as quarterstaffs still applies to the others regardless.
Whether a +1 Spell Focus (Staff) can necessarily be used as a +1 Quarterstaff for weapon attacks isn't answered, possibly simply because a +1 Spell Focus (staff or otherwise) isn't actually a thing that exists in general (though, specific named staffs or foci like the Staff of Power may include +'s that are explicitly limited to weapon attacks). For a DM navigating that question in a situation where they've handed out a +1 Spell Focus (Staff), for parity's sake, I would humbly suggest that they treat it the same as they would for a Warlock with Improved Pact Weapon using a +1 Quarterstaff as a spell focus... which, based on the description of Weapon, +1 applying to attack and damage rolls "made with" the item, I think clearly would apply to spell attacks and damage using it as a focus.
Room for disagreement there, but it's the simplest reading of +1 Weapon, and agree or disagree about the intent it's equally supported by the text, and I don't see any reason to treat a magical enhancement as more effective going weapon -> focus than a similar enhancement going focus -> weapon.
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I'm going to make this way harder than it needs to be.
Thinking about this one, I'm not sure where to draw the line.
Would you allow duelling style to work if the character was holding a sword in the second hand, ? Probably not.
How about spellcasting focus orb or a component pouch? Probably yes.
How about a frying pan?
A brick?
A rolled up cloak?
A gnome?
Sometimes I'm baffled by how far people will try to look at ultra specific wording to affect rulings in a game where the DM literally just makes everything up on the fly. You don't gain benefit from Duellist if you are holding another weapon in your other weapon. A staff is a weapon, whether you call it a quarter staff or a staff. Bear in mind when applying your thinking that under the Monk class, you're specifically allowed to rename weapons to whatever you want and they are still weapons. If your monk calls his offhand weapon a Moon Pie that doesn't change the fact that it's actually a dagger. The game rules are designed around people applying good sense to them (because DnD is a game of infinite possibilities) and not rules lawyers.
If you are holding a staff in your second hand, you are holding a weapon in that hand. It's clearly a weapon. You know it's a weapon, because if you were disarmed of your sword, you would wield the staff. You even reference Gandalf in the LOTR movies, who we see whacking orcs with it... as a weapon. If you hit someone with it, everyone would say "They hit that guy with a weapon," not "they hit that gut with a six foot long wooden arcane focus." If you made your arcane focus a "four foot long metal blade" then it's a sword even if you are calling it by a different name.
Use common sense for these things. The rules are there to help you tell magnificent stories.
Can you fight with a sword in one hand and a staff in the other? Sure. Can you gain Duellist bonus? No. You're very specifically breaking the one condition that prevents you gaining Duellist bonus.
To make this work for you in your campaign: agree with your DM that your arcane focus is not considered a quarterstaff because it's too light, and if ever it's used in combat it will count as an Improvised Weapon (termed in the PHB as "anything that doesn't resemble a weapon that can be wielded in one or two hands."). Technically the arcane focus staff does resemble a weapon, but by being too light, it can be counted like any other object as improvised. If ever you use it in combat it would therefore count as Improvised and therefore deals only 1d4 damage. Duellist says you cannot have a Weapon in your other hand... but anything in the world that you can pick up can be used as an improvised weapon. Clearly you can be a Duellist with a sword in one hand and a bottle or bunch of flowers in the other (you can even have a shield). You still won't be able to make bonus action two-weapon-fighting attacks with it in any case, as it's not a Light Weapon anyway.
Duelist only requires you to be wielding only 1 weapon, it doesn't restrict you from benefiting from it while holding a weapon you are not using in your other hand. I said as much 4 days ago.