Relax, it's not all bad, there are just a few details that I don't feel fit the world.
To be frank, I have looked at your CS before and noted some of these things since day 1. However, I believe that criticizing an unfinished idea is not only counter-creative but also premature. Some ideas sound weird if you only hear half of them, but will make sense once all the info is there. I don't want you to feel like you've wasted any time on this character

To start out, the name – Grover. Would it be rude to ask for an asian-sounding name? You can still keep Grover as the proxy name for whatever that thing is that infested your character.

Robot - This is really the big one. I can't say how clear I've been with my description of the world, but the way I imagined it is pretty much a medieval asian setting. Bringing a robot into it just feels wrong. It would be so out of place, a thousand years or more ahead of its time.
With that said I like the way you've built the character to fit with the idea, and I'm getting a real Orochimaru (Naruto) vibe from the guy, which is something you don't see very often.
To be constructive, and not just a bitch, how do you feel about making a small change from robot to some kind of Venom-like (Spider-man) parasite? It would still allow for all the stuff you've written, but would fit the world a bit better.

Special traits – You're kind of stacking the advantages here.
Note: What I am NOT saying is; lose the bullshit, dipshit.
What I AM saying is; this will affect the game.

Sea Dweller – What?
Propellers, above and below… Are you flying? Why stay away from the water? What is going on?

First things first. He is not a robot. More like he got a permanent metal encasing as a skin, permanent armor. His legs when he transforms are like that to allow him to achieve greater speed and to increase supportibility of his weoght.But inside he's all flesh and blood and mush. So same as the venom concept you mentioned except with a constant metal armor. To say one last thing on this, even if he had 0 metal on him, all his limbs and such would function the same except look more fleshy. So same as the nymph who got metallic claws as weapons he got metalic body armor.

And about sea dweller... The basic concept was that he could swim fast by rotating limbs as propellers. But that seems a lot like transformers now that I think about it.

Now that I explained, if it still bothers you I'll go with the venom idea you proposed. And I also changed the special traits. If you have a problem with one in particular tell me and I'll remove it.

This explanation makes a lot of sense, and is pretty close to how you described the power in your character. What got me was that you wrote robot as gender. It made me wonder about what your character concept really was and I just wanted to make sure.

The problem with sea dweller was simply that I couldn't picture what was going on, I won't tell you to remove it or anything, but perhaps you could describe it a bit better?

Special traits were all fine. Having many advantages simply means that whoever you use them on will quickly realise what's going on and try to get help. The Inquisition would truly be interested in someone like that ;)

You could also add something about the characters brain-smarts under skills and abilities, but you don't have to.