This app was mentioned in 3 comments, with an average of 2.67 upvotes
My best recollection is that Undefeated's storyline is not especially weird. The enemies are mutated, but the story isn't especially weird and the enemy artwork is doesn't feel particularly strange. If you want weirdness in your RPGs, I recommend Fearless Fantasy ($3.99). I'll note that it uses active turn-based combat.
Fearless Fantasy is kind of similar in that it's a turn-based RPG with timing-based attacks and whatnot. It's got nowhere near as much charm as the Mario & Luigi RPGs but it's fun nevertheless.