Serene Horizon

This land enters tapped.

If you control at least three other piercers, this land
is a 4/3 blue and green elemental in addition to its other types, it is still a land.

{t}, {g}{u}: Slypierce. (When you Slypierce, target blue creature you control gains your choice of either hexproof, flash, protection from one color of your choice, or ward {2}.)