The Prince of Beasts

At the beginning of your upkeep, if your life total
is greater than half your maximum life total.
Otherwise, transform The Prince of Beasts.
When this creature transforms into The Prince
of Beasts, you may pay {b}{b}{b}. If you do, each
opponent sacrifices the creature with the highest
mana value among creatures they control. Each
opponent that can't loses 10 life.