Obuun, Mul Daya Ancestor

At the begginning of combat on your turn, up to
one target land you control becomes an X/X
Elemental creature with trample and haste
until end of turn, where X is Obuun's power.
It's still a land.
Landfall - Whenever a land enters the battlefield
under your control, put a +1/+1 counter on
target creature.