Krenko, Mob Instigator

When Krenko, Mob Instigator enters the battlefield, attacks, or dies, Goblin amass X, where X is the number of other Goblins you control. (Put X +1/+1 counters on an Army
you control. If you don't control one, create a
0 /0 red Goblin Army creature token first.)
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"Get 'em."