Calamity

Calamity is a legendary hand crossbow for the Demon Hunter in Diablo III. It requires character level 60 to drop.

This Hand Crossbow was considered one of the most valuable in game because of its ability to apply Marked for Death (for free!) to every enemy its bearer hits, regardless of the Proc Coefficient, effectively boosting total damage done by 15% without wasting a skill slot. This effect does benefit from runes and enhancements of the original skill (as of 2.4.2).

In return, this Hand Crossbow is the rarest hand crossbow to drop: to get one from Kadala, a Demon Hunter would theoretically need approximately 50,000 Blood Shards, which is (statistically) enough to gamble the full Embodiment of the Marauder set four times.