Cheapest priced copy (Commander 2020): $0.59 at Card Kingdom, near mint, their price list as of .
Adriana, Captain of the Guard 
Legendary Creature — Human Knight · 4/4 · Rare · Phyrexia: All Will Be One Commander · #114
Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Other creatures you control have melee. (If a creature has multiple instances of melee, each triggers separately.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $0.59 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2020 | 200 | Rare | $0.59 | — |
| Conspiracy: Take the Crown | 73 | Rare | $0.79 | $11.99 |
| Dominaria United Commander | 139 | Rare | $0.59 | — |
| Phyrexia: All Will Be One Commander | 114 | Rare | $0.59 | — |
4 rulings from Wizards of the Coast
- 23 August 2016Melee will trigger if the creature with melee attacks a planeswalker. However, the effect counts only opponents (and not planeswalkers) that you attacked with a creature when determining the bonus.
- 23 August 2016Creatures that enter the battlefield attacking were never declared as attackers, so they won't count toward melee's effect. Similarly, if a creature with melee enters the battlefield attacking, melee won't trigger.
- 23 August 2016You determine the size of the bonus as the melee ability resolves. Count each opponent that you attacked with one or more creatures. It doesn't matter if the attacking creatures are still attacking or even if they are still on the battlefield. It also doesn't matter if the opponent you attacked is still in the game.
- 23 August 2016It doesn't matter how many creatures you attacked a player with, only that you attacked a player with at least one creature. For example, if you attack one player with Wings of the Guard and another player with five creatures, Wings of the Guard will get +2/+2 until end of turn.