Mags, Uttercold Apprentice

Defender
Whenever Mags, Uttercold Apprentice blocks a
creature, put an uttercold counter on that
creature. For as long as that creature has an uttercold counter on it, it has "This creature
doesn't untap during its controller's untap step.
When this creature is dealt damage, destroy it."
(The creature remains frozen after Mags,
Uttercold Apprentice has left the battlefield.)