The rune of Sarlacc destroys any mobs and items dropped on it. If a mob is killed at the edge and its drops fall outside the rune, they won't be destroyed.
Strictly speaking it's not a bug, but I see how this could be abused to get both drops and double XP, so I'll look into fixing it. However, it may take a while since I don't have much time right now.
Xilef11
commented
5 years ago
The rune of Sarlacc destroys any mobs and items dropped on it. If a mob is killed at the edge and its drops fall outside the rune, they won't be destroyed.
Strictly speaking it's not a bug, but I see how this could be abused to get both drops and double XP, so I'll look into fixing it. However, it may take a while since I don't have much time right now.