Cactaeqqus

Ride {r/w}{w/b} ({r/w}{w/b}: Put this and target creature you control in a single mutate pile. Humans in the pile with vigilance have Horsemanship.)
Whenever Cactaeqqus rides or becomes tapped put a -1/-1 counter on a creature you control.
"Only sadists, self-flagellants, or the out-of-body can even consider it." — Elise