Mindvine Hydra

Mindvine Hydra's power and toughness are equal to the amount of forests you control.
When Mindvine Hydra enters the battlefield, pair it with a creature. When the paired creature dies, flip a coin. The winner of the flip pairs Mindvine Hydra with another creature. The controller of the paired creature controls Mindvine Hydra.
"You are mine, and the world is yours."