Cheapest priced copy (The Lost Caverns of Ixalan Commander): $1.99 at Card Kingdom, near mint, their price list as of .
Master of the Pearl Trident 
Creature — Merfolk · 2/2 · Rare · Magic 2013 · #59
Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $1.99 to $84.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Merfolk vs. Goblins | 9 | Rare | $2.79 | — |
| The Lost Caverns of Ixalan Commander | 162 | Rare | $1.99 | — |
| Magic 2013 | 59 | Rare | $2.79 | $29.99Out of stock |
| Time Spiral Remastered | 310 | Special | $2.79 | $84.99 |
One ruling from Wizards of the Coast
- 19 March 2021Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to a Merfolk you control may become lethal if Master of the Pearl Trident leaves the battlefield during that turn.