Fairy Tail
Fairy's Heart: This gives you a 25% chance of revival back to 25% health instead of being killed.
Lamia Scale
Shed Skin: When under 25% health there's a chance for you to shed your skin removing all status effects on you.
Blue Pegasus
Winged Speed: When under 25% health you move at 2x speed.
Mermaid Heel
Mermaids Charm: When under 25% health, a male enemy who damages you has a chance of being stunned for a couple of seconds.
Quattro Cerberus
Wild Mode: When under 25% health. All damage you deal is 25% stronger.
Raven Tail
Raven Flap: When under 25% health, there,s a chance to teleport around an enemy who damages you, messing up their aim.
SabreTooth
Fist Of The Tiger: When under 25% health your punch speed is doubled.
Phantom Lord
Phantom Phase: When under 25% health theres a chance that you will temporarily become invisible