Wand of draining
As usual for wands, the beam from a wand of draining zapped by the player has a power rating of (30 + 2d(Evocations skill)).
As with any other wand, the bolt of draining projected by a wand of draining in the hands of a monster uses a power rating of (30 + (monster hit dice)). This gives it a typical damage output of 3d8 when used by low-level monsters and 3d9 when used by mid-to-high level monsters, and the player needs EV 19 to have a 50% chance of evading the beam without Repel or Deflect Missiles in force.
Tips & Tricks
As a tier-1 attack wand, wands of draining provide a powerful backup attack. Melee characters should save them for living opponents that are unusually dangerous to engage in melee, such as hydras and acidic monsters. Ice Magic and Fire Magic users should use them as a backup or alternate attack against living opponents that resist their elemental attack spells; very few living monsters have any Life Protection at all.