Cheapest priced copy (Battlebond): $0.35 at Card Kingdom, near mint, their price list as of .
Proud Mentor 
Creature — Human Warrior · 1/1 · Uncommon · Battlebond · #20
Partner with Impetuous Protege (When this creature enters, target player may put Impetuous Protege into their hand from their library, then shuffle.)
{W}, {T}: Tap target creature.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battlebond | 20 | Uncommon | $0.35 | $0.49 |
| Battlebond Promos | 20s | Uncommon | — | $0.39 |
3 rulings from Wizards of the Coast
- 8 June 2018A nonlegendary creature can't be your commander, even if it has a "partner with" ability.
- 8 June 2018Note that the target player searches their library (which may be affected by effects such as that of Stranglehold) and that the card they find is revealed, even though these words aren't included in the ability's reminder text.
- 8 June 2018"Partner with [name]" represents two abilities. The first is a triggered ability: "When this permanent enters the battlefield, target player may search their library for a card named [name], reveal it, put it into their hand, then shuffle their library."