Madtrip

Aura of Decay — At the beginning of your end
step, put a -1/-1 counter on each other creature.
Compounded Sickness — If a source would deal
damage to a creature with a -1/-1 counter on it,
it deals double that damage to that creature
instead.
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The Madtrip's only love is decay, which it inflicts
with voracious delight.
Artwork/creature source:
https://www.youtube.com/watch?v=7FpLmuGXrKs