Ion, the Electromagnetic Golem
I am not going to go into scalings as I am really not good at balancing those kinds of things. Overall this champion is an AP tank who is low damage but can conditionally amp up his damage with proper positioning (you'll see how when I mention the skills).
Passive: This champion counts as terrain in addition to being a unit (For example, Vayne can use him for her condemn or an ally/enemy nautilus can Q him to pull himself the full way).
Q: Plasma shot--- Active: Fires a ball of energy in a skill shot. This energy ball can bounce off of terrain up to two times (can hit the same target multiple times). Deals magic damage.
W: Monopole--- Passive (magnetic shield): Takes reduced damage from ranged attacks. This passive is lost when ability is on cooldown. Active: Tosses a large floating ball at target area. This ball acts as terrain. Units moving away from said ball gain movement speed, units moving towards it are slowed; this champion himself however, has the reverse effect. (Basic combo, toss monopole behind enemy; then shoot Q so that it bounces off the ball and yourself hitting the enemy a total of 3 times. Of course the enemy can move messing up the combo). It doesn't deal any damage, or should deal only very little damage; but it should have a really good range.
E: Charged Shrapnel--- Active: Fires charged shrapnel in a short ranged spread (enemies closer take more damage as opposed to further away enemies that only get hit by a single piece). Shrapnel can bounce off of terrain one time. Enemies hit by shrapnel once are slowed. Enemies hit by shrapnel twice are stunned.
R: Transcend---- Active: Becomes a being of pure energy firing himself in a skillshot dealing magic damage to any enemies he passes through. If while in his energy form he collides with terrain, he roots himself in place and his ult cooldown is reset for 2 seconds (as in it goes to back to the full cooldown if you don't use it right away). This cooldown's reset is limited to 3 times (maybe reduce it to 2 if it's too powerful?). This should be pretty slow moving and fairly easy to dodge when not in a major team battle. Should have some nice range to it, but not global.
Some issues with the kit. The synergy with Jarvan ult might be too strong, the worse part is he can synergize with a Jarvan ult even if it's the enemy's. On the other hand, he can't exactly get on the inside of a Jarvan ult to help an ally either; at least not without flash. I could also see Azir being the ultimate counter, as none of his abilities can go through an Azir ult.