Aerythella the Arousing

At the beginning of your upkeep, every thrall under your control gains flying until the end of your turn. After this effect resolves, you may tap Aerythella and pay {b}{u}: target enemy creature with resilience less than 2x Aerythella’s power. That creature comes under your control as a thrall and loses -1/-1. Aerythells gains +1/+1.
As long as Aerythella has control of at least two thralls, she has flying. As long as Aerythella has control of at least three thralls, she has vigilance.