Well its a superpredator. Billy Brennan Illustrated by Jesper Ejsing Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
Here's an example from Standard that I encountered very recently
Adventures have their own name, mana cost, type line (including the new instant and sorcery subtype Adventure), and rules text
But in Duskmourn: House Of Horror's Death Toll Commander deck, a card in your graveyard can be many things
(Create a token thats a copy of a creature token you control.) Whenever a creature token you control enters, put a +1/+1 counter on this creature
In the end, From Under the Floorboards takes the prize, for the relatively simple, but still horrible scenario it presents - just a trio of nasty zombies bursting up into your home to eat you