Cheapest priced copy (Modern Horizons): $0.35 at Card Kingdom, near mint, their price list as of .
First Sliver's Chosen 
Creature — Sliver · 3/3 · Uncommon · Modern Horizons · #9
Sliver creatures you control have exalted. (Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each instance of exalted among permanents you control.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Horizons | 9 | Uncommon | $0.35 | $2.99 |
2 rulings from Wizards of the Coast
- 14 June 2019Whenever a creature you control attacks alone, count the number of instances of exalted among permanents you control. After those abilities resolve, that’s how many times the creature will get +1/+1.
- 14 June 2019A creature attacks alone if it’s the only creature declared as an attacker during the declare attackers step (including creatures controlled by your teammates, if applicable). For example, exalted won’t trigger if you attack with multiple creatures and all but one of them are removed from combat.