Monsieur Rat, Plague Bringer

At the beginning of your endstep, all players
dealt damage by a rat creature you control
get a flea emblem. (Flea emblems have, at
the beginning of your upkeep lose 1 life)

All loss of life from flea emblems is treated as
commander damage from Monsieur Rat if
he is your commander

Rats in your graveyard have the name, slime
Against humanity.