Equilibrium

• WWizards of the Coast2008-04-01
  Official Ruling
  A "creature spell" is any spell with the type Creature, even if it has other types such as Artifact or Enchantment. Older cards of type Summon are also Creature spells.
• WWizards of the Coast2008-08-01
  Official Ruling
  The ability is put on the stack immediately after you cast a creature spell, which means the creature that spell will become won't be a legal target.
• WWizards of the Coast2008-08-01
  Official Ruling
  The ability will still resolve even if the spell that triggered it gets countered.

Rulings via Scryfall