Cheapest priced copy (The Brothers' War): $1.79 at Card Kingdom, near mint, their price list as of .
Sarinth Greatwurm 
Creature — Wurm · 7/6 · Mythic · The Brothers' War · #358
Trample
Whenever a land enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $1.79 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War | 220 | Mythic | $1.79 | $2.49 |
| The Brothers' War | 358 | Mythic | $2.79 | $2.49 |
| The Brothers' War Promos | 220p | Mythic | $2.99Out of stock | $2.99Out of stock |
| The Brothers' War Promos | 220s | Mythic | — | $2.79Out of stock |
4 rulings from Wizards of the Coast
- 14 October 2022Sarinth Greatwurm's second ability triggers whenever a land enters the battlefield under any player's control, not just under your control.
- 14 October 2022Powerstone tokens are a kind of predefined token. Each one has the artifact subtype "Powerstone" and the ability "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell."
- 14 October 2022Although all the cards in The Brothers' War that create Powerstone tokens create a tapped Powerstone token, entering the battlefield tapped isn't part of the token's definition. Notably, if you create a token that is a copy of a Powerstone token, the token copy won't enter the battlefield tapped.
- 14 October 2022You can use the {C} added by a Powerstone token on anything that isn't a nonartifact spell. This includes paying costs to activate abilities of both artifact and nonartifact permanents, paying ward costs, and so on.