Cheapest priced copy (Ikoria: Lair of Behemoths): $0.35 at Card Kingdom, near mint, their price list as of .
Archipelagore 
Creature — Leviathan · 7/7 · Uncommon · Ikoria: Lair of Behemoths · #283
Mutate {5}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, tap up to X target creatures, where X is the number of times this creature has mutated. Those creatures don't untap during their controller's next untap step.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ikoria: Lair of Behemoths | 41 | Uncommon | $0.35 | $0.49 |
| Ikoria: Lair of Behemoths | 283 | Uncommon | $0.35 | $0.79 |
One ruling from Wizards of the Coast
- 17 April 2020Archipelagore’s triggered ability can target a creature that’s already tapped. That creature won’t untap during its controller’s next untap step.