Abyss Watcher

A deck can have any number of cards named Abyss Watcher.
Whenever three or more cards named Abyss Watcher attack, each Abyss Watcher can't be blocked this turn.
Whenever eight or more cards named Abyss Watcher attack, each Abyss Watcher gains indestructible, lifelink, and double strike until end of turn.