You have resistance to cold damage while you hold this staff.

Spellcasting. The staff has 10 charges. While holding it, you can use an action to expend 1 or more of its charges to cast one of the following spells from it, using your spell save DC: cone of cold (5 charges), fog cloud (1 charge), ice storm (4 charges), or wall of ice (5 charges).
The staff regains 1d6 + 4 expended charges daily at dawn.

Devour Soul. Once per day when a spell cast with the staff kills a creature, that is not a construct or undead, the staff can absorb the killed creatures soul to regain spellcasting charges. The number of charges corresponds to the size of the creature killed. Tiny 1d3, Small 1d4, Medium 1d6, Large 1d8, Huge 1d10, Gargantuan 1d12, if the creature has a spellcasting ability the staff recharges an additional 1d4 charges.
These charges can take the staff over its maximum of 10, while the total charges are above 10 at the start of your turn you take a number of d4 cold damage equal to the number of charges over 10. This cold damage ignores damage resistance. At the start of each of your turns after that it increase by 1d4 until the remaining charges return to 10 or lower. A creature who's soul has been absorbed can only be restored to life by a wish spell.

This long black metal staff, ending in three spikes pointed towards a centre orb of ice, radiates a cold aura. A grey handle wrapping is the only place the staff can be held comfortably. The staff holds the soul of a wizard who greatly encourages killing.

Notes: Resistance: Cold, Druid, Sorcerer, Warlock, or Wizard, Damage, Control, Combat, Warding