Deep Magic Volume 2 (p.194)
Last Strike
1-level Abjuration
Casting Time: 1 reaction, which you take when you drop to 0 hit points as a result of taking damage
Range/Area: Self
Components: Verbal, Somatic
Duration: 1 round
Damage/Effect: Buff
You grant yourself a last burst of energy when deeply wounded. Before you fall unconscious, you gain one action. Any roll you make, such as for an ability check or attack roll, has advantage. You automatically fail your first death saving throw.
Available for: Cleric, Paladin, Wizard