The Dark crystal (prayer drain) is one of the debuff crystals dropped by bosses during Morvran's Slayer challenge. It is not dropped by any specific monster. The crystal doubles the rate at which prayers and curses drain prayer points.
When attempting to destroy any dark crystal, the player will not be able to progress in Morvran's Slayer challenge unless they are carrying all dark crystals earned so far while killing the next boss. Destroying the crystal will make the player have to reclaim it from Morvran to continue in the challenge.
Dark crystals | |
|---|---|
| Dark | |
| Black crystals |
 Magic weakness Melee weakness No ultimates/specials Ranged weakness Reduced healing Reduced magic Reduced melee Reduced ranged |
