Cheapest priced copy (Lorwyn Eclipsed): $0.49 at Card Kingdom, near mint, their price list as of .
Kinscaer Sentry 
Creature — Kithkin Soldier · 2/2 · Rare · Lorwyn Eclipsed Promos · #22p
First strike, lifelink
Whenever this creature attacks, you may put a creature card with mana value X or less from your hand onto the battlefield tapped and attacking, where X is the number of attacking creatures you control.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
3 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Lorwyn Eclipsed | 22 | Rare | $0.49 | $0.79 |
| Lorwyn Eclipsed | 300 | Rare | $0.69 | $1.49 |
| Lorwyn Eclipsed Promos | 22p | Rare | $1.29 | $0.79 |
4 rulings from Wizards of the Coast
- 17 November 2025Although the creatures put onto the battlefield with Kinscaer Sentry enter as attacking creatures, they were never declared as attacking creatures. Abilities that trigger whenever a creature attacks won't trigger when the creatures enter attacking.
- 17 November 2025You choose the player, planeswalker, or battle the creature you put onto the battlefield is attacking. It doesn't have to attack the same player, planeswalker, or battle as Kinscaer Sentry.
- 17 November 2025The value of X is calculated only once, as Kinscaer Sentry's last ability resolves.
- 17 November 2025If a card in your hand has {X} in its mana cost, X is 0 for the purpose of determining its mana value.