Martyr's Rally 2014

3rd-level enchantment

Casting time: 1 reaction, which you take when you are reduced to 0 hit points
Range: Self
Components: V
Duration: 1 minute

With a hopeful rallying cry just as you fall unconscious, you rouse your allies to action. Each ally within 60 feet of you that can see and hear you has advantage on attack rolls for the duration. If you regain hit points, the spell immediately ends.

Source: Tome of Heroes (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details