Celestial Unicorn

Flying 4W: Creatures you control get +1/+1 until end of turn.

Vigilance Constellation — Whenever this creature or another enchantment you control enters, choose target creature you control. Until end of turn, that creature has base power and toughness 4/4 and gains flying.

When this creature enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.) As long as it's your turn, this creature has first strike.

Vigilance Whenever one or more +1/+1 counters are put on this creature, put a +1/+1 counter on each other creature you control. This ability triggers only once each turn.

(T: Add B.)

Whenever another creature you control enters, you gain 1 life.

This spell costs 1 less to cast for each spell your opponents have cast this turn. Scry 2, then draw two cards. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

This creature can't be blocked. When this creature enters, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)