Cheapest priced copy (Ixalan): $0.79 at Card Kingdom, near mint, their price list as of .
Jace's Sentinel 
Creature — Merfolk Warrior · 1/3 · Uncommon · Ixalan · #283
As long as you control a Jace planeswalker, this creature gets +1/+0 and can't be blocked.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ixalan | 283 | Uncommon | $0.79 | — |