You can't cast Beastie Beatdown unless you choose a creature you control and a creature an opponent controls as targets.
2024-09-20 • wotc
If either creature is an illegal target as Beastie Beatdown tries to resolve, the creature you control won't deal damage. If the creature you control is an illegal target, you won't put two +1/+1 counters on it even if you have delirium.
2024-09-20 • wotc