Cheapest priced copy (The List): $8.99 at Card Kingdom, near mint, their price list as of .
Cavalier of Night 
Creature — Elemental Knight · 4/5 · Mythic · Core Set 2020 · #94
Lifelink
When this creature enters, you may sacrifice another creature. When you do, destroy target creature an opponent controls.
When this creature dies, return target creature card with mana value 3 or less from your graveyard to the battlefield.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $8.99 to $27.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 94 | Mythic | $9.49 | $27.99 |
| The List | M20-94 | Mythic | $8.99 | — |
| Core Set 2020 Promos | 94p | Mythic | $21.99 | $24.99 |
| Core Set 2020 Promos | 94s | Mythic | — | $20.99 |
4 rulings from Wizards of the Coast
- 12 July 2019Cavalier of Night’s enters-the-battlefield ability goes on the stack without a target. While that ability is resolving, you may sacrifice another creature. When you do, the reflexive triggered ability triggers and you pick a target creature to be destroyed. This is different from effects that say “If you do . . .” in that players may take actions after you’ve sacrificed the creature but before the target creature is destroyed.
- 12 July 2019If a card in a graveyard has {X} in its mana cost, X is considered to be 0.
- 12 July 2019If a creature card with mana value 3 or less becomes a copy of Cavalier of Night, its last ability can target itself when it dies.
- 12 July 2019While resolving Cavalier of Night’s enters-the-battlefield ability, you can’t sacrifice more than one creature.