Niblis of Frost [Eldritch Moon] Zendikar Tawnos finally cracked the puzzle:

Tawnos finally cracked the puzzle: the strange structures did not house Mishra's malevolent creations but were themselves among his creations

The form of the sigil is just as important as the sigil itself

if it's the second creature spell you cast this turn

" —Gerrard Capashen

Niblis of Frost [Eldritch Moon] Zendikar Tawnos finally cracked the puzzle:Set: Eldritch Moon Type: Creature Spirit Rarity: Rare Cost: {2}{U}{U} Flying Prowess (Whenever you cast a noncreature spell, this creature gets +1 +1 until end of turn.) Whenever you cast an instant or sorcery spell, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.