Staff of Withering

From Dungeon Master's Guide, page 205. Found on Magic Item Table G.

Description
''Staff, rare (requires attunement by a cleric, druid, or warlock). 4 lbs.''

This staff has 3 charges and regains 1d3 expended charges daily at dawn.

The staff can be wielded as a magic quarterstaff. On a hit, it deals damage as a normal quarterstaff, and you can expend 1 charge to deal an extra 2d10 necrotic damage to the target. In addition, the target must succeed on a DC 15 Constitution saving throw or have disadvantage for 1 hour on any ability check or saving throw that uses Strength or Constitution.