First off, I want to know if this is a game breaking idea. The first thought that comes to mind, is a barbarian constantly jumping in front of the way for the bard. I'm looking more for the tension of self sacrifice.
I would assume it would be a reaction, but i'm not too sure on how to execute it. Any suggestions?
It would be sort of broken imo, because it messes with the action economy in subtle ways. Essentially what this does is not only allows a creature to take the dash action, but it allows them to take it out of turn as a reaction. That is a lot of movement that your beefy characters are going to want to take for positioning reasons, and is giving them a movement action for not a whole lot
Comparably the only other way to move using your reaction is to ready an action on your turn and choosing the dash action, sacrificing your entire action in order to move when some event triggers. As such I would work within that framework, and instead of making a new ability, I'd remember that creatures of the same size provide half cover. Using this knowledge, a character could already choose to forgo their action in order to ready a dash, with the trigger being that an ally is being attacked with a ranged attack. Then the DM could give your ally half cover bonuses, and just rule that if the roll to hit would not hit them but hit you, then the attack hits you instead.
If you want to guarantee that the attack is redirected, then you could just make a special action type that has to be readied to use. Making the character eat a melee attack is trickier though because you can't willingly end your move in an occupied space...so that said you'd have to add the rider that the one using this ability has to simply move through the allies space to grant the benefit to the ally, which adds a tactical layer to it.
EDIT: Or simpler, just make it to where if you move through an allies space when they are being attacked, the attack is redirected to your character. No real big rules changes or long paragraphs to add, and makes it clear that to use it you have to ready it because you can't normally move out of turn...but it also frees it up so that the battlemaster fighter can do some cool things like ready an action and use maneuvering attack to move an ally to eat a blow on another character with the trigger being to attack the nearest enemy when they see an ally being attacked by anyone. It'd add interesting tactical depth doing it that way which would be pretty cool and not broken imo.
I would consider either trying to get the protection fighting style (level 1 fighter, level 2 paladin), or make a homebrew feat (or house rule reaction) based on it. You could also just make a feat that gives a fighting style.
Protection
When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.
I would consider either trying to get the protection fighting style (level 1 fighter, level 2 paladin), or make a homebrew feat (or house rule reaction) based on it. You could also just make a feat that gives a fighting style.
Protection
When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.
I like that, but the OP was also looking at the tension of self-sacrifice. What about a Feat that allows using your reaction to take the damage, either in whole or in part? There's no self-sacrifice if you just make the enemy miss.
"When a creature within 5 feet of you is hit, you can use your reaction to transfer the damage to yourself." (or..."to transfer half of the damage to yourself.")
If that's too powerful, also give yourself disadvantage on your next action, or the next enemy attack against you at advantage, or your friend you took the damage for has disadvantage on their next action (because you had to recklessly jump in front of your buddy at the last second, so now you're off balance, or you shoved them and now they are off balance.)
First off, I want to know if this is a game breaking idea. The first thought that comes to mind, is a barbarian constantly jumping in front of the way for the bard. I'm looking more for the tension of self sacrifice.
I would assume it would be a reaction, but i'm not too sure on how to execute it. Any suggestions?
It would be sort of broken imo, because it messes with the action economy in subtle ways. Essentially what this does is not only allows a creature to take the dash action, but it allows them to take it out of turn as a reaction. That is a lot of movement that your beefy characters are going to want to take for positioning reasons, and is giving them a movement action for not a whole lot
Comparably the only other way to move using your reaction is to ready an action on your turn and choosing the dash action, sacrificing your entire action in order to move when some event triggers. As such I would work within that framework, and instead of making a new ability, I'd remember that creatures of the same size provide half cover. Using this knowledge, a character could already choose to forgo their action in order to ready a dash, with the trigger being that an ally is being attacked with a ranged attack. Then the DM could give your ally half cover bonuses, and just rule that if the roll to hit would not hit them but hit you, then the attack hits you instead.
If you want to guarantee that the attack is redirected, then you could just make a special action type that has to be readied to use. Making the character eat a melee attack is trickier though because you can't willingly end your move in an occupied space...so that said you'd have to add the rider that the one using this ability has to simply move through the allies space to grant the benefit to the ally, which adds a tactical layer to it.
EDIT: Or simpler, just make it to where if you move through an allies space when they are being attacked, the attack is redirected to your character. No real big rules changes or long paragraphs to add, and makes it clear that to use it you have to ready it because you can't normally move out of turn...but it also frees it up so that the battlemaster fighter can do some cool things like ready an action and use maneuvering attack to move an ally to eat a blow on another character with the trigger being to attack the nearest enemy when they see an ally being attacked by anyone. It'd add interesting tactical depth doing it that way which would be pretty cool and not broken imo.
I would consider either trying to get the protection fighting style (level 1 fighter, level 2 paladin), or make a homebrew feat (or house rule reaction) based on it. You could also just make a feat that gives a fighting style.
I like that, but the OP was also looking at the tension of self-sacrifice. What about a Feat that allows using your reaction to take the damage, either in whole or in part? There's no self-sacrifice if you just make the enemy miss.
"When a creature within 5 feet of you is hit, you can use your reaction to transfer the damage to yourself." (or..."to transfer half of the damage to yourself.")
If that's too powerful, also give yourself disadvantage on your next action, or the next enemy attack against you at advantage, or your friend you took the damage for has disadvantage on their next action (because you had to recklessly jump in front of your buddy at the last second, so now you're off balance, or you shoved them and now they are off balance.)
Looking for new subclasses, spells, magic items, feats, and races? Opinions welcome :)