There are reports of getting a letter from Skulvar Sable-Hilt, after going on a killing spree in Whiterun. In one confirmed case, the Dragonborn killed the two stuck Alik'r warriors just inside the gates of Whiterun in broad daylight, and paid the guards off using their Thieves Guild connections. Later in Markarth a courier delivered a letter asking to "call on him" when the Dragonborn is in Whiterun. Attacking and feeding on certain characters will also lead to receiving the letter. After receiving the letter, the Dragonborn must first drop the letter and read it again to receive the quest to go attack Jervar, killing him is not necessary. After that, they will reveive 50 gold from Skulvar.
He claims that the horse he sells to the Dragonborn is named "Queen Alsiger or Allie for short".
If the Dragonborn successfully or fails to sneak on him he will start a conversation and give them a sword.