Vertigo Spawn

• WOTC Official Reminder Textofficial rules
  Defender — This creature can't attack.

• WWizards of the Coast2006-02-01
  Official Ruling
  If the creature was already tapped when Vertigo Spawn blocked it, that creature still won't untap during its controller's next untap step.
• WWizards of the Coast2006-02-01
  Official Ruling
  If two Vertigo Spawns block the same creature, both abilities trigger, but each only affects the creature during its controller's next untap step. The creature can untap during its controller's untap step following that one.

Rulings via Scryfall