Horn of Heimdallr

Creatures you control get +0/+2 and vigilance.
Whenever a creature enters the battlefield under
an opponent's control, put a watch counter on
Horn of Heimdallr.
Remove X watch counters, {t}: Reveal the top 5
cards of your library. You may put a creature
card with converted mana cost X or less from
among them onto the battlefield. Put the rest on
the bottom of your library in a random order.