Natara, the Overflowing Sun

At the beginning of each opponent's upkeep, you
may put a flood counter on target non-Island
land that player controls.
Lands with flood counters are Islands in addition
to their other types. (They have: "{t} add {u}.")
At the beginning of your upkeep, you gain X life
and distribute X +1/+1 counters among creatures
you control, where X is the number of Islands on
the battlefield.