#kanima master

Theory 1: Harris

Well it could be Harris. The show does a good job of placing him - or at least his car at many of the scenes

in 2x05

The sheriff tells us tire tracks matching his car was found at the scene where the couple was killed/hurt

Harris was at the rave (spotted by Matt and Allison) and Stiles saw his car outside. 

But what is Harris' motive? Who does he want to kill? There is no obvious connection to Matt, so if he's his accomplice then i have no idea what the reason might be. 

He's show more than average concern for Jackson on multiple occasions though, so perhaps becoming his "master" could be an attempt to keep him safe? 

In 1x05 after he was clawed by Peter

Harris: Hey, Jackson. If you need to leave early for any reason, you let me know.

And also in 2x07 when Jackson is clearly being "activated" by Matt to try and scare the others off his case. He gets a headache in detention

Harris looks very concerned. Notice the First Aid kit behind him. Is he really honestly trying to help Jackson? To counter what Matt is trying to do?

And he actually follows him out, wanting to make sure he is okay. 

Notice the fire extinguisher on the wall next to him. Is that what Harris is trying to do? 

There is little doubt that Harris knows about the supernatural. I also find it strange how he deliberate place all of them in detention when only a Scott and Jackson deserved it. Was it to test something? 

I just know that we get another shot of his bumper sticker as he leaves the school

And a strange scene of him leaving the premises and looking around and also checking the mirror. Mirrors always signify change of some kind. And notice how he stares directly at us. 

So theory 1:  Harris is actually trying to be the kanima's friend and not master. But Matt's hold on him is stronger. 

Theory 2: Gerard 

Gerard is also a hot candidate for someone auditioning to replace the current kanima master. 

2x06: 

You can clearly see Gerard holding his hand out, palm up. It's not an agressive move. It's actually greeting it, offering his hand - his "friendship."

There isn't physical touch here because a moment later Scott barrels into the kanima, but the intention was clearly conveyed. And Gerard certainly has a murder he wants to avenge, namely Kate. 

And Gerard basically admits to Chris later that he wants to get to Derek and he intends to get someone else = the kanima to do it for him. 

Chris: You know what I'm having trouble believing? How you just stood there while that thing circled you, and did nothing. You want to explain that to me?  Gerard: Intuition.  Chris: Then you know what it is.  Gerard: I have a suspicion. And if I'm right, it plays by certain rules. Rules that don't bend easily.  Chris: Do we need to put a hold on Derek to figure this thing out?  Gerard: Not necessarily. Tonight's the first time you had a glimpse of him since Kate died, am I right?  Chris: Unfortunately.  Gerard: And the only other tie we have to him is Isaac Lahey.  Chris: What are you thinking?  Gerard: That if this thing bothers Derek enough to bring him out of his little hole, then we might have an opportunity. What did I teach you is the best way to eliminate a threat?  Chris: Get someone to do it for you.

Look at the phrase I put in italics above. 

It plays by certain rules. Rules that don't bend easily.

As a seasoned hunter Gerard knows this. It even says so in the bestiary. It's a instrument for vengeance. Sure Matt has read this as well (he copied Lydia's translation) but its doubtful he knows that these are set rules. 

Stiles: So all the people you've killed so far - Jackson: Deserved it. Stiles: See, we got a little rule book that says you only go after murderers. Jackson: Anything can break if enough pressure's applied.

That last line there - that doesn't sound like anything Matt would say. It sounds more like how Gerard talks. Watch Matt's monologue on what happened to him in 2x10 and you get a better sense of how he talks. It's straightforward and youthful. Now Gerard on the other hand is prone to more "colorful" sentences. Like "Something wicked this way comes" etc. 

Deaton: Hold on. The book says they're bonded, right? What if the fear of water isn't coming from Jackson, but from the person controlling him? What if something that affects the kanima also affects its master?

Mountain Ash would affect the kanima. That is why Stiles spreads mountain ash all around the building in 2x08 and successfully activates it. We see that Erica and Isaac can't cross it. 

If Deaton's right then Matt shouldn't be able to cross it either. But we never see Matt leave the building while the mountain ash line is active, so we don't really know for sure. 

But we do get this

Gerard does notice the mountain ash. And he holds his hand above it and has a small reaction. Almost as if it gave him an electric shock. 

This could be an indication that Gerard is also partially in control of the kanima and the mountain ash line affects him.

We know that he hasn't started taking the mountain ash pills yet. Scott switches them out in 2x10 at the Sheriff station. 

Theory 3: All of the above. 

I mean why the heck not? Matt is clearly the strong and in control master of the kanima. The formed the bond first and so far he's only killed people connected to the swim team. 

Gerard has made an offer and is either on the waiting list or he hasn't chosen to "activate" jackson for his own purposes yet. He's lining up his pieces getting ready for checkmate

2x08 Raving

Allison: It didn't work. None of it, none of it worked.  Gerard: Oh, I wouldn't say that. In fact, I'd say the prognosis isn't nearly as dire as it seems. Not nearly.

And Harris might be trying to actually be the kanima's "friend" and not master. he does show unusual interest and care for Jackson's well being.

And they're all present at the rave.