<PATIENCE, DEMONTOUCHED. The conduit is too weak to channel my full power--I require time to transfer it into you. Allow me to delay these insects while I do so. We can crush them once I am realized.>
Mordred already let me in control, so roll to keep it. Assuming he doesn't win the fight, start on my below spiel:
Mordred's eyes go wide, and he stares at the blade "Y-yes, [name], I'm a reflection of Blastel! I--he split his soul into two halves and forced one into this idiot!" [If Blastel isn't actually a mage:]"I, I mean, we, we used the magic knife to do it."[/notmage] "I've conquered this guy's mind and rendered him incapable of harming anyone! Please don't kill me, it'll kill both of us--that Blastel and this Blastel!" Mordred looks at Blastel "Confirm it for him so we don't die!"
If Blastel starts to flub the confirmation, immediately hand control back to Mordred while telling him to kill the swordsman while he's distracted, and pump all my magic towards enhancing whatever action Mordred takes.
If Blastel doesn't flub it, continue:
Mordred heaves a sigh of relief. "Now then, like I said, I looked into this idiot's mind, and found out that he brought his family along. His wife's got a pretty valuable jeweled ring--I don't know how they got it, yet--and both the wife and daughter are very attractive." A lecherous grin spreads across Mordred's face.
Lastly, still charging his telekinesis. If his other wound is bad enough to weaken him, work on clotting it, but don't rush it.
((So, Comrade, here's the big problem with this char. It is a separate character from yours, but only one of us can control the body at a time--if we disagree on a course of action, we have to actually fight over it. If we manage to agree, you essentially get a bunch of strong buffs in addition to your regular abilities, plus the ability to temporarily lose control and gain +2 cha and +1 will, but these advantages come at the cost of potentially losing control when you don't want to. Generally, I'd rather avoid forcing control, but if I think something is a really bad idea, the knife'll force things.
If that's too much of a cost, I can probably just take over Blastel (or one of the other bandits), assuming they're left alive, but you lose the buffs in that case. The knife can only cast on people who have contact with it.))