Gimmicky planeswalkers are ones that have a twist to them, only having negative abilities, maybe being an uncommon walker, a nonlegendary one, one centered around only zeroes, one that transforms, one that has a plus that can get it to an ult directly by adding loyalty counters, etc
For a normal set, this might be overwhelming, but in Ravnica, where only five color pairs (and the five arcs of their intersections) are supported, this could be exactly what the doctor ordered
It also cares about enchantments entering the battlefield rather than being cast, which means blink shenanigans or returning enchantments from your graveyard to play (think Replenish) are going to be impactful
Illustrated by Dan Murayama Scott Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Not Legal Comp
Tacking on the Root Sliver ability of not being able to counter the creature or any future creatures is certainly powerful as well
This is of Common rarity