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.)
Adriana turns a wide creature board into an explosive attack by giving your whole team melee, rewarding you for attacking multiple opponents at once. Flood the board with tokens or aggressive creatures, then swing at every opponent simultaneously so each attacker gets a stacking +1/+1 buff. The more opponents you hit, the larger your army becomes mid-combat, letting you close games out of nowhere.
Free, scaling anthem effect that grows your entire board the more opponents you attack
Cheap to abuse with go-wide token strategies in efficient Boros colors
Combat math is brutal for opponents who can't block multiple swinging armies
Rewards multiplayer politics—incentivizes spreading attacks across the table
Melee only triggers on attack, so she does nothing on defense or against control sweepers
Highly vulnerable to board wipes that erase your token army
Boros lacks card draw and ramp, leading to running out of gas
Single removal spell on Adriana shuts off the team anthem