Cheapest priced copy (Assassin's Creed): $0.39 at Card Kingdom, near mint, their price list as of .
Headsplitter 
Artifact — Equipment · Common · Assassin's Creed · #289
When this Equipment enters, create a 1/1 black Assassin creature token with menace, then attach this Equipment to it.
Equipped creature gets +1/+0.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.39 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Assassin's Creed | 289 | Common | $0.39 | — |
3 rulings from Wizards of the Coast
- 5 July 2024The Assassin token that you create enters the battlefield as a 1/1 creature. Any abilities that trigger when a creature with a certain power enters the battlefield will see the token enter as a 1/1 creature. Static abilities that affect the Assassin's power and toughness may change this.
- 5 July 2024No player may take any actions between the time you create the Assassin token and the time Headsplitter becomes attached to it.
- 5 July 2024If the triggered ability causes two Assassins to be created (due to an effect such as that of Doubling Season), Headsplitter becomes attached to one of them.