Foe Sirvente is a song in Final Fantasy XI. It is available only to Bards who have reached 75 and have gained enough additional Merit points, then designated that they wish to learn this ability. It is a tier two skill. As such, it may be initially purchased for 3 points, and then upgraded twice for 4 and then 5 points.
Foe Sirvente, in a way, is the cardinal opposite of the other 75 Bard Merit song, Adventurer's Dirge. Foe Sirvente is a single target song. The affected player character will lose enmity at a decreased rate than normal. In other words, this song is used to help the tank keep the attention of the enemy creature.