Cheapest priced copy (Commander 2021): $2.79 at Card Kingdom, foil, near mint, their price list as of .
Felisa, Fang of Silverquill 
Legendary Creature — Vampire Wizard · 3/2 · Mythic · Commander Legends: Battle for Baldur's Gate · #845
Flying
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever a nontoken creature you control dies, if it had counters on it, create X tapped 2/1 white and black Inkling creature tokens with flying, where X is the number of counters it had on it.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $2.79 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2021 | 2 | Mythic | — | $2.79 |
| Commander 2021 | 329 | Mythic | $7.99 | — |
| Commander Legends: Battle for Baldur's Gate | 845 | Mythic | $2.79 | — |
4 rulings from Wizards of the Coast
- 16 April 2021If the creature with mentor leaves the battlefield with mentor on the stack, use its power as that creature last existed on the battlefield to determine whether the target creature has less power.
- 16 April 2021If the target creature's power is no longer less than the attacking creature's power as the ability resolves, mentor doesn't add a +1/+1 counter. For example, if two 3/3 creatures with mentor attack and both mentor triggers target the same 2/2 creature, the first to resolve puts a +1/+1 counter on it and the second does nothing.
- 16 April 2021Mentor compares the power of the creature with mentor with that of the target creature at two different times: once as the triggered ability is put onto the stack, and once as the triggered ability resolves. If you wish to raise a creature's power so its mentor ability can target a bigger creature, the last chance you have to do so is during the beginning of combat step.
- 16 April 2021The last ability counts the number of all kinds of counters, not just +1/+1 counters.