Let's say these are Gen 8's starters, somewhat reimaginings of the Gen 1 starters. A quadruped dino thing, a bipedal lizard, and a bipedal tortoise.

>Why does he wear the mask?
Their theme/motif for the starters this Gen are superheroes/supervillains, so they wear masks. Fire evolves into the "hero", Water evolves into the "villain", and Grass evolves into an "antihero" or neutral thing.

Which one you picking?