Cheapest priced copy (Innistrad: Midnight Hunt): $1.79 at Card Kingdom, near mint, their price list as of .
The Celestus 
Legendary Artifact · Rare · Innistrad: Midnight Hunt · #252
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.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $1.79 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 252 | Rare | $2.29Out of stock | $11.99 |
| Innistrad: Midnight Hunt | 252 | Rare | $1.79 | $2.49 |
| Innistrad: Midnight Hunt | 377 | Rare | $2.29 | $1.99Out of stock |
| Innistrad: Midnight Hunt Promos | 252p | Rare | $1.79 | $3.49 |
| Innistrad: Midnight Hunt Promos | 252s | Rare | — | $2.49 |
6 rulings from Wizards of the Coast
- 24 September 2021If it is night, and the active player of the previous turn cast two or more spells during their turn, it becomes day.
- 24 September 2021If a triggered ability triggers whenever day becomes night or night becomes day, it only triggers if it was already either day/night and becomes the other. It does not trigger when the game becomes day or night for the first time.
- 24 September 2021If it is day, and the active player of the previous turn cast no spells during their turn, it becomes night.
- 24 September 2021Before a player untaps their permanents during the untap step, the game checks to see if the day/night designation should change.
- 24 September 2021Day and night are designations that the game itself can have. The game starts as neither. Once the game becomes day (or less commonly, night), the game will be exactly one of them—day or night—going back and forth for the rest of the game.
- 24 September 2021If you choose to draw a card with The Celestus but some effect replaces that card draw with something else, you will still have to discard a card.