The Isle of Bloob

The Isle of Bloob enters the battlefield tapped.
{t}: Add {u} or {g} to your mana pool.
As long as you control no other creatures, The
Isle of Bloob becomes a 1/5 Elemental creature.
It is still a land.
To travelers, he is a safe haven. Against invaders, he
is a staunch defender. The islanders simply know him
as "Bob."