From DDO wiki
Mortal Fear: On Hit: 8 to 64 Force Damage. In addition, 5% chance to cut non-boss foe's current health in half.
- found on Tier 3 Thunder-Forged weapons.
- After around Update 23, it no longer works on Orange named enemies. No mention on Release Notes (stealth nerf).
- As of Update 29, the effect that does 50% hit point damage no longer functions in Legendary (CR31+) quests or raids.
- Axerwannabe's Mortal Fear video, pre-U23, Warlock Sobrien seen here is Orange named.