From the files of the KNIGHTS, Martyn Muller

Martyn Muller, known aliases include Matthew Muller, Martin Miller, the Haunter of Halingehn, Reget, Sir Real, and Marvin Patrick.
Adult male Endlyrian, brown hair and eyes. Distinctive features include thick eyebrows and an outdated prosthetic hand (left), electrical battery rather than laaka.
Citizenship is East Endlyrian, now revoked.
Fluent in Terran, Endlyrian and Halish.
Kinetic. Abnormal ability set. Mr. Muller is able to  make himself and whatever he is in contact with insubstantial, able to move through other objects while still being observed. From our previous interactions we can confirm that he is able to control what is still solid to him, explaining why he does not simply fall through the floor. Except when he wants to. He is able to discontinue this insubstantiality at a time of his choosing, or after a short duration, usually some 4 or 5 seconds, after he has lost contact with the item. At this point the object will be able to interact with the rest of the world as normal, intersecting with anything it was in the same space as. If an object "solidifies" for want of a better term, inside of another, then there is no lasting damage to the integrity of either, but it appears that fluid and gaseous exchange is limited. To use the example of the most common circumstance, someone's limb that is caught in a wall would still be able to move, but would be affixed at the point of intersection and suffer reduced circulation. Luckily comparable effects that could move an object non-linearly, say for example teleportation or another stint of insubstantial movement, can remove the object without any further damage than it has suffered, and the short duration he imparts on an object is fixed, once he lets go there are a few seconds that could be used to prevent suffocation.
Claims to have developed his kinesis following exposure to laaka (weapons grade kerit), further inspection advised as this is highly unlikely, and contrary to current hypothesis. Nonetheless, Mr. Muller seems to have some vulnerability to its presence, and exposure heavily limits his control over his current state.

Additional:

• Talented Laaka engineer, even if he can't touch the stuff. Current dependence may cause a problem.
• Normally unwilling or unable to use firearms.
• Prefers to avoid a fight unless he started it. Understandable, as his ability is most dangerous in a surprise or as an escape route.
• Little formal training in hand to hand combat, relies almost exclusively on what advantages his power affords him.
• Do not underestimate; has engaged multiple senior KNIGHTs.
• Uses multiple guises.
• Known links to the gangs of the Ajaddi.

File 18-5-7-5-20
The following is an interview with key KNIGHTs, transcript of an earlier recording in the event of file corruption.
Paul: This is the first log for the discussion of methods for combating kinetic criminals. Take 2. Hello, my name is Paul *Audio Corrupted* I'm the one who wrote this if you could tell.
Aaron: They probably can.
Paul: So, this is the interview tape for dealing with Martyn Muller. I was the first one of us to have any contact with him for an extended period. He's remarkably calm when not trying to kill you. He didn't recognise us at first, thought we were just some kids trespassing where we didn't belong. He'd managed to catch me by surprise, stuck my hands through the floor. Its odd. Sort of tingly I'd say, its most likely the nerves firing. Surprisingly your limbs still work if they've been intersected, muscles and nerves still work, circulation is restricted rather than stopped.
Aaron: He likes to go for your hands. For one I'd say its because Sparrow cost him one of his own, but a lot of kinetics seem to need to wave their hands all over the place to do anything.
Paul: Its a learned method that aids in concentration and helps to-
Aaron: He's got that same weakness though, can't make you intangible, that's the one right?
Paul: I prefer insubstantial but-
Aaron: He can't pull you with him unless he's touching you. And between a mask, shoes, and a prosthetic all he's got for that is his right hand. Keep blocking that. Sparrow found it out as well, just keep yourself inside his space if he tries to avoid you too long, stops him from getting a breath in. What else...
Paul: There's his reaction to Laaka, I believe it extends to weaponry from what you've told me.
Aaron: Laaka guns. They don't hit him if he's untouchable, but it hurts from what I've seen. My piece does the worst, but even a miss with a normal one can break his concentration. Got anything to add Sparrow?
Sparrow: This man makes me sick.
Paul: Ok, we can leave it there for today.
Sparrow: He has it out for me, and I don't know if he hates Duhnkengagen too, but he isn't exactly going easy with the slurs. Its not as if he doesn't know what he's saying. Its bait, I know its bait, but people like him? They've been after me since I was a kid. And he's just chasing revenge for... I'm out.
Paul: Wait we can-
Aaron: I don't think she's coming back. Should we finish up or?
Paul: No I think we're done, besides these things take three people we should-
Sparrow: Here's Laz. Knock yourselves out.
Lazarus: Cool, do I finally get to do one of these?
Paul: Sparrow I know-
Aaron: She's going to forget how to use a doorknob one of these days.
Lazarus: She ain't coming back. So... Who are we talking about?
Paul: Martyn Muller, alias the Haunter of Halingehn, alias-
Aaron: That idiot in the mask that keeps trying to kill Sparrow.
Lazarus: You mean that Ender who walks through walls?
Paul: The former East Endlyrian who-
Lazarus: Cos he's pretty bad at it. Killing Sparrow, not the walls thing.
Aaron: Yeah but he's dangerous, and He's persistant.
Lazarus: And he won't give up.
Aaron: Laz that's 
Lazarus: I know I know I'm just messing with you.
Paul: So if you were in a fight-
Lazarus: I remember now, I got his-
Paul: Lazarus, in your experience what can you offer about staging a confrontation with the kinetic criminal Martyn Muller, and the threat posed by his abilities?
Lazarus: Ok ok, no need to yell. Um... Get him talking. He's worse than Paul if you can get him going, and he can't stay untouchable and talk. That and he'll waste breath instead of chasing you.
Aaron: Call him Martyn. Ask about the mask. He has a whole speech prepared.
Lazarus: I think we caught him practising once?
Aaron: So yeah, untouchable though, dodges as long as he can concentrate, distractions work, same as Sparrow.
Paul: That concludes our-
Lazarus: Its a real good thing she didn't hear that.
Paul: This concludes our interview on Martyn Muller.
Aaron: She's going to end up listening to this isn't she.