The Celestus

If it's neither day nor night, it becomes day as The Celestus enters.
{T}: Add one mana of any color.
{3}, {T}: If it's night, it becomes day. Otherwise, it becomes night. Activate only as a sorcery.
Whenever day becomes night or night becomes day, you gain 1 life. You may draw a card. If you do, discard a card.

Obsessive Astronomer

If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, discard up to two cards, then draw that many cards.

Sunstreak Phoenix

Flying
If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, you may pay {1}{R}. If you do, return this card from your graveyard to the battlefield tapped.

Firmament Sage

If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, draw a card.

Into the Night

It becomes night. Discard any number of cards, then draw that many cards plus one.

Component Collector

If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, you may tap or untap target nonland permanent.

Vadrik, Astral Archmage

If it's neither day nor night, it becomes day as Vadrik enters.
Instant and sorcery spells you cast cost {X} less to cast, where X is Vadrik's power.
Whenever day becomes night or night becomes day, put a +1/+1 counter on Vadrik.

Brimstone Vandal

Menace (This creature can't be blocked except by two or more creatures.)
If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, this creature deals 1 damage to each opponent.