Hey there! :)
Looks like you're setting off making a champion concept, want a few points in the right direction?
Q-
So what does his Q do? Because it has two different descriptions from the sound of it. It:
-Places a sigil that stuns enemies in a small aoe.
-Leaping dash that grants movespeed.
If you wanted to combine the two one thing you could do is having him leap to his sigil after it goes off. That can also be what applies the stun, but this depends on whether he's meant to be an offensive or defensive tank.
Either way, this ability sounds pretty fair in and of itself. It reminds me of Swain's snaring zone.
W-
Doesn't sound terribly useful for a tank. This is more of a diver/assassin ability. Generally, tanks are only mobile enough to get to a fight. Once they're in they tend to be immobile, especially when it comes to getting back out.
E-
I assume you mean he completely controls the enemy. This would be an interesting form of crowd control, but it's VERY easy for it to be broken. You COULD make it very short ranged and an ultimate if you're sold on this idea, but I'd suggest thinking of something else. You could make this into a limited mind control that forces the enemy to do something specific briefly instead of controlling them directly. Like make them run past Orven, for instance.
R-
The description is a bit vague, what does this actually do? ^^;
The concept of him getting more benefits for placing his sigils is interesting, though. If you're going to do this, I'd suggest retooling his W or E so that they also make sigils, so that it's a bit easier for him to stack them on the map.
Passive-
Interesting idea, though I'd suggest putting this on a cooldown, and also limit it to only when he lands the killing blow. This would work even if he were a support since he could still get it off the relic shield procs.
As for whether it's useful beyond the stat bonus he gets to go along with it, I'm not terribly sure. Lets him build up a minion advantage in lane but it's pretty useless aside from that.
It's not a bad start and he has a clear thematic of controlling both the battlefield and enemies with his sigils, so what you need to do now is iron out his gameplay style. I'd suggest working off his Q and giving him a style of going in and seizing "control" (hypothetically in controlling the fight via cc) of fights. The basics of what his Q, E, and ultimate do works - though his E and ultimate could do with some fleshing out - but his W and passive could use a change of direction. For his W at least, I'd strongly suggest giving him some sort of point blank delayed effect to chain with his Q or to dissuade enemies trying to pick fights with his allies when he's around.
Oh, and if you want to make him work as a tank, he needs one or two forms of durability built into his kit. Almost every close-range champion who's not a carry or assassin has one.
Examples:
Zac's blob pickups
Sion's exploding shield
Sejuani's frost armor
Vi's passive shield
Irelia's cc reduction and self-healing off her W and ultimate
Warwick's self-healing from his Q and ultimate and the damage reduction on his E.
Hope this all helps, best of luck with Orven!
, and then get a small, short, speed boost. Does small amount of True Damage.