At the beginning of your upkeep, put a -1/-1 counter on Mini Goku.

{T}Remove all counters from Mini Goku: You may pay {R}{R}{R}{W}{W}{W}{W}. If you do, transform Mini Goku. Activate only if Mini Goku has no -1/-1 counters on it.

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Mini goku, Demon Realm beast

Legendary Creature — Saiyan Great ape

Whenever Mini Goku, Demon Realm Beast deals combat damage to a player, put a +1/+1 counter on it. Then you may pay {X}, where X is no greater than the number of +1/+1 counters on it. When you do, destroy X target nonland permanents.

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