You've learned to put the weight of a weapon to your advantage, letting its momentum empower your strikes. You gain the following benefits:
On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.
Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.
In reading that. My DM and I are having a debate on the meaning of the second bullet point. I'm playing a 5th level Paladin who uses primarily a Great Axe. So our questions are:
AM I able to use the -5 to hit and +10 damage on any attack roll or just one throughout my turn as I have 2 attacks per turn with extra attack.
Does this cost me my bonus action to use the -5 to hit and +10 damage?
Can I use the -5 to hit +10 damage on an opportunity attack?
You can use it for any melee attack with a heavy weapon you're proficient with. There is no limit on uses and it doesn't require an Action or Bonus Action, you just have to declare it before you roll to hit.
Yeah so no "Oh, I rolled a 19, I use Great Weapon Master". You have to declare it before the roll. So if you would have hit without using the ability but you used it and you don't hit, well, too bad.
You can use it on one, two or all of them if you have ways to attack more then twice through Fighter Extra Attack at levels 11-20, Bonus Action attacks through Polearm Master/Haste/Two-Weapon Fighting, etc.
You get to choose for each attack.
I don't know if you ever played previous editions but this is 5E's equivalent of Power Attack which was also free of action resources but had to declare ahead of time.
The only conditions for the use of the -5/+10 are "Before you make a melee attack with a heavy weapon that you are proficient with". It can be used any time you are making a qualified attack, regardless of whose turn it is, or how many attacks you make on your turn etc. If it was meant to be limited to only your turn(Extra Attack), or only once on your turn(Giant's Might), it would say so.
As great weapon master reads:
You've learned to put the weight of a weapon to your advantage, letting its momentum empower your strikes. You gain the following benefits:
In reading that. My DM and I are having a debate on the meaning of the second bullet point. I'm playing a 5th level Paladin who uses primarily a Great Axe. So our questions are:
AM I able to use the -5 to hit and +10 damage on any attack roll or just one throughout my turn as I have 2 attacks per turn with extra attack.
Does this cost me my bonus action to use the -5 to hit and +10 damage?
Can I use the -5 to hit +10 damage on an opportunity attack?
You can use it for any melee attack with a heavy weapon you're proficient with. There is no limit on uses and it doesn't require an Action or Bonus Action, you just have to declare it before you roll to hit.
Yeah so no "Oh, I rolled a 19, I use Great Weapon Master". You have to declare it before the roll. So if you would have hit without using the ability but you used it and you don't hit, well, too bad.
You can use it on one, two or all of them if you have ways to attack more then twice through Fighter Extra Attack at levels 11-20, Bonus Action attacks through Polearm Master/Haste/Two-Weapon Fighting, etc.
You get to choose for each attack.
I don't know if you ever played previous editions but this is 5E's equivalent of Power Attack which was also free of action resources but had to declare ahead of time.
You can as well
The only conditions for the use of the -5/+10 are "Before you make a melee attack with a heavy weapon that you are proficient with". It can be used any time you are making a qualified attack, regardless of whose turn it is, or how many attacks you make on your turn etc. If it was meant to be limited to only your turn(Extra Attack), or only once on your turn(Giant's Might), it would say so.
could i use the -5 to hit +10 to damage multiple times on one hit? like could i do -15 to hit +30 to damage? thats what it seems like to me
No. It says "you may choose to take -5 hit". If you could take more than -5 to hit for additional damage, it'd have to say so explicitly.