Thankfully Imgor wasn't looking in Alex' direction as the flare ignited, so he remained unaffected.
With the knife in his hands, he attempted to circle the beast, using the tracking spell to know its position while he did his best to not be noticed by the beast. If he could successfully get behind the beast, he would grab its stinger, jab a knife into a joint of its tail, turn the knife sideways to cut through most of the joint, and then rip off the stinger, in case it was still connected. Without its stinger, the beast had lost one weapon, and in case Imgor wouldn't loose the stinger in the battle, he also had a poisonous weapon for future fights.
The beast would most likely try to attack him the instant he grabbed the stinger. He would have to get away from the beast as quickly as possible, if he didn't want to end up as beast-food.