This is my take on UF LB (Underfell: Till Death[Wip name] or A-a! Underfell: Last Breath)

Inspiration- i think i remembered Fruit saying smth about this, i think not completely sure.

What Happens?

Most likely not obvious but this is Phase 2... mhm.

Sans begins to get more and more tired from his constant dodging, then, you seemingly land a hit on Sans but he appears unscathed. Gaster then fades infront of Sans,now stepping in to defend Sans , Sans now glad to know Gaster is here, he decides to rest.

Gaster does most of the fighting in phase 2, Sans sometimes jumping in to help, and for phase 3... it's being thought out rn so can't confirm anything yet.