Abyss Watchers

Doublestrike, Haste, Vigilance
At the beginning of combat on each of your turns create one 3/4 Abyss Watchers creature token with Doublestrike, Haste and Vigilance.
At the beginning of combat on each of your turns if your Life is half or less than half your starting life total, sacrifice all Abyss Watcher Creature tokens Abyss Watcher gains power and toughness equal to the power