On the other hand interesting design although it reminded me of an evil version of Lucian... I like the idea of the ultimate but I don't think it's fair for him to control the enemies's spirit...
-and he doesn't control enemies spirit. maybe I didn't actually know how to put it in words for the ultimate. So here goes, Rosendo blast his enemy Malphite (example), and malphite soul comes out...malphite will still control his own soul, if he move back to his body, the stun effect will be gone and he is freed from the ulti. So Rosendo doesn't control anything, this ultimate is for team fights, sometimes we don't actually know where we are when teamfights occurs as there's alot of stuff going on, this ulti can shoot out the soul of enemy and confuse the enemy for abit.
Here's what I think about his Q: Maybe his rest of his abilities work together properly, from blinking to pull and grab to stun and full-mode auto-attack. Then he cast his Q where his ability deals most damage from the BACK while the enemy is actually in the front! Unless of course you could aim it to the back so the backshot hits the enemy instead but still... I think it's a bit odd for a skill.
For a champion I think he would be great! But too OP if you ask me XD. Still great though!
As for Q, the shoot back will have a delay after the first shot is out, so when blink in, most likely to face back of the opponent and shoot. This skill is meant for opponent on the front and the back, like you can deal damage on both of them on the same time.
Anyways, thanks for your time to write such long comments
Wow, pretty interesting concept for both Rosendo and Marosen. I like the idea that they are one and the same and that if one dies to the other, the latter gets something. Its kind of like the quest for Rengar and Kha'Zix, so I see where you were coming from with the buff. I think the reward for the quest could use some tweaking, maybe not a buff but something else. The idea that summoners choose which champ they go with for their account is also a very good concept too - adds more preference to the game and then interaction too.
Overall, both sound like they would be awesome to play