Enemy who's supposed to have high endurance

[Hungry Chao]

I'm trying to create a boss battle, but the enemy storywise is supposed to be particularly resilient and difficult to kill. My problem is coming up with a more creative way of portraying this characteristic in a boss battle than him just being a massive damage sponge

 

[Andar]

Low damage rates for the damage elements. If you make them different low rates the player would have to find which weapons/skill do the most damage

 

[headdie]

You could do a multiple phase battle which changes up how the boss fights, perhaps throw some dialogue in between phases to break up the gameplay loop and if you are feeling generous trigger save points so the player isnt left frustrated if they loose during a long boss fight.

 

[Wavelength]

I would use enemy behavior conditions to get the boss to use high-effectiveness protective moves (perhaps applying a state to himself that massively reduces damage for a few turns or creating a construct that must be destroyed before he can take any further damage) at certain points in the battle (whether it's on a certain turn, or better yet, once his HP has dropped below certain points).

Also, don't underestimate the power of in-battle dialogue to get your point across.  Having the boss say something that implies he's gritty right before he uses that protective move, and then having your characters chatter over the next turn or two about how hard he is to finish off for good, will give the battle a lot of identity.

 

[Eschaton]

In the first Mass Effect game you would fight against krogan, a race known for their resilience. Mechanically, this translated into enemy krogan having high health regen and also having the equivalent of Auto-Life (both suspiciously absent from your own krogan party member).

I don't know if this is how you'd want to do it in your game, but the above mechanics did help to convey krogan not only as dangerous but notoriously difficult to kill.

 

[OM3GA-Z3RO]

In the first Mass Effect game you would fight against krogan, a race known for their resilience. Mechanically, this translated into enemy krogan having high health regen and also having the equivalent of Auto-Life (both suspiciously absent from your own krogan party member).

I don't know if this is how you'd want to do it in your game, but the above mechanics did help to convey krogan not only as dangerous but notoriously difficult to kill.

Not unless you have toxic ammo which cancels out their Auto-Life.

But OP, if you want to make a resilient boss there are plenty of ways to do it, just like Eschaton said he could have a high health regen in which you have to pour all your OP skills out on it or maybe like figure out how to slow down it's mass regen or you could just make him have high defense with some sort of hidden weakness or have a high HP pool that maybe some mixture of something will trigger some sort of damage combustion. The ideas and potential are endless if you just put your mind to it