You tap your staff on the ground, and acid boils up to envelop your target in a caustic haze.
Encounter ✦ Acid, Arcane, Implement Standard Action Ranged 10 Target: One creature
Attack: Intelligence vs. Reflex
Hit: 1d6 + Intelligence modifier acid damage. Until the end of your next turn, creatures more than 5 squares away from the target have concealment against it.
Staff of Defense: The next time you use the Staff of Defense class feature before the end of the encounter, the attacker also takes acid damage equal to your Intelligence modifier.