'Darkest Fears is a technique appearing in Kingdom Hearts 3D: Dream Drop Distance.
Mechanics
Darkest Fears is a Single Link used by Riku. While activated, Riku will grow claws of Darkness, which he attacks with instead of his keyblade. His combo's consist of him rapidly slashing and cutting at the enemy, and the finisher has him surging at the enemy. Towards the end of the combo, his claws will glow Red.