Pernicious Skulker

Mutate {3}{b} (If you cast this spell for its mutate
cost, put it over or under target non-Human creature
you own. They mutate into the creature on top plus all
abilities from under it.)
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Each time this creature mutates put a +X/+X on
target creature you control where X is the
number of lands and noncreature spells you
control on the battlefield.
as Gideon Jura ran, it was bound to be swifter.