Nephalian Kelpie

Bestow {3}{g/u}, forestwalk, islandwalk
Enchanted creature gets +1/+2 and has islandwalk and forestwalk. Whenever it deals damage to a player, they reveal the top card of their library. If it's a Forest or an Island, destroy enchanted creature and put a +1/+1 counter on Nephalian Kelpie.
"A magnificent steed, but a treacherous one."