Yggdrasil, World Tree

When Yggdrasil, World Tree enters the battlefield, sacrifice it unless you sacrifice
creatures with total power 5 or less.
Yggdrasil, World Tree enters the battlefield tapped.
At the beginning of your upkeep, if
Yggdrasil, World Tree has less than 3 eternity counters
on it, put on it number of eternity counters equal to the difference.
{ut}: Add one mana of any color to your mana pool.
Remove an eternity counter from Yggdrasil, World Tree: Untap it.