The Leviathan

The Leviathan has indestructible as long as you
are at or above half your starting life total.
At the beginning of each opponent's upkeep, that player puts a flood counter on a land that player controls without a flood counter on it.
When The Leviathan attacks, it gains trample
and gets +1/+1 until end of turn for each land defending player controls with a flood counter
on it.