Isran asks the Dragonborn to find and destroy the vampire masquerading as a Visiting Advisor to the Jarl of a radiant city. However, to avoid slandering the Dawnguard's name, permission must be gained from the Jarl to kill the creature or the guards will see it as murder. During battle, the Advisors will cast Vampiric Drain and Ice Storm. With low Magicka remaining, they will cast Ice Spike repeatedly along with Vampiric Drain. When their Magicka pool runs dry, they will switch to their enchanted dagger and use Vampiric Drain on occasion until their Magicka regenerates, and the process continues until they are defeated.
Gunmar asks the Dragonborn to find and destroy a vampire masquerading as a Visiting Advisor in a radiant city. However, unlike Isran or Gunmar's other disguised targets, there is no option to get permission, or have the target follow the Dragonborn to a secluded location. The kill must be made at risk of a bounty.