Dual "Ice Climbers" Champion.
This is an idea I've had for a while now for a champion. I think it's unique and interesting enough to fit in with Riot's recent philosophy of making sure new champions play incredibly unique, though whether it would work in practice is iffy. I won't get bogged down in numbers because I feel like it's most important to get the core ideas down and I've never been the best with those things.
The basic idea is that you have 2 people at once: the normal champion and the 'pet' they have around constantly, a la malzahar's voidlings. We'll call the main champ Alice and the secondary champ Bob. Cool? Well, controlling 2 characters is a bit difficult, but it can also be incredibly powerful. To supplement this we need to make sure neither character is particularly powerful on their own. Additionally, we have to put certain mechanics around Bob that: A: diversify different strategic possibilities by different positioning of Alice and Bob both relative to each other and their surroundings. B: Allow ample room for counter play from the opponent. C: Create room for varied build paths.
If what you see so far is to your liking, up vote this so that Riot can see. What I'm going to post here is one possible way you can go about this.
As far as the behavior of Bob, I have a few ideas. First of all, if he goes too far away from Alice, he will start taking damage until he dies and cannot perform any actions other than moving closer to Alice. Secondly, as normal, Alice deals physical damage with her basic attacks (and her abilities) that scales with AD (she deals less than a normal champ would be herself). Bob deals magic damage that scales with level and AP. In other words, investing in AP improves Bob and his magic damage, while investing in AD improves Alice and her physical damage.
As far as their other stats, They share Armor and MR (sort of) and Bob's HP is based on level +some% of Alice's bonus HP. movement speed is shared between them, as is AS and tenacity.
When Bob dies, he respawns after some time, lets say 16/14/12/10 seconds scaling on rank of the ultimate. This is because, in the late game, there should be less counter-play involved with killing Bob to keep him away for a long time (though it should still be a factor)
Passive: Alice has less MR than she normally would and more Armor (lets say 90% and 120%) while Bob has less armor and more MR. This gives each of them a more strategic niche in the overall game-plan of you and your enemy's.
Q: Alice and Bob each slash all enemies immediately in front of them, damaging (either physical or magic) and applying a slow. Enemies hit by both do not receive double damage or a slow, but they do take true damage instead of magic or physical. This does a number of things, chiefly that there are different options. Do you have them focus on one enemy and maximize damage, or do they spread out and slow/aoe the most? This encourages control over Bob and proper decision making. This move will have a higher than expected cool down, but it will decrease by some amount (.5-1 second) every time either one of them lands a basic attack. Additionally, it has a higher than normal mana cost, which is addressed by their next ability.
W: Only usable while both Alice and Bob are immediately next to each other. They channel for 2-3 seconds (I dunno maybe they hold hands as a magic circle appears around them or something), after which they both regain health, mana, and they both gain a large movement speed buff that decays over a few seconds. This makes keeping Bob around crucial for sustain in lane and helps them prepare for team fights by getting into position. It can't be thrown out willy-nilly though. It gives a powerful incentive to make sure Bob is alive in lane while also giving incentive for the opponent to take him out. I also didn't want to overload them with combat abilities in fear of them getting too overwhelming. It also scales with AP. Due to Alice being around more often than Bob and her scaling with AD, players would normally get more mileage out of building AD. This gives incentive to consider building AP as well.
E: This is where things get interesting.This is their movement ability. By clicking on Alice, Bob, or somewhere else on the map, one of 3 things will happen: 1: Bob flies towards Alice, dealing magic damage to all enemies he flies through and knocking them briefly towards Alice. Alice and Bob, upon meeting up, both get a buff in MR. No buff is applied if this movement is stopped by hard CC. 2: Alice flies onwards Bob, dealing physical damage, knocking back enemies, and applying an armor buff to both of them. 3: Alice and Bob fly towards each other, dealing physical and magic damage respectfully and knocking enemies in the direction they travel. They both stop upon meeting each other, at which point they both get a buff to AS. This gives them a lot of options for escaping and for team fights. If an enemy with a lot of physical damage targets where Bob is? Have Alice fly in and add some heavy armor into the mix. The same goes for Bob and MR. With the third option, they bring enemies towards where they are and gain a lot of attack speed. When doing this they naturally end up back to back, allowing them to use Q and auto attacks that bring Q up more frequently to deal with multiple enemies during a team fight. Of course, only one of these can be chosen, so you must choose wisely. If Alice is alone, she can still give herself either the MR or AS buff, but no movement or attack is done.
R: Alice dashes a fixed distance towards target point, dealing physical damage to enemies she passes. A second cast causes Bob to perform the same action towards another target point. A third cast causes both of them to dash towards another point. Enemies hit by this receive a stack. Upon reaching 3 stacks, an enemy is stunned. If Bob is not present, Alice still can perform 2 dashes. This emphasizes positioning and mastery over both champions into fighting and offers a much more versatile form of mobility than E. Additionally, Alice is that much less helpless even without Bob, having essentially a toned down spirit rush on a higher cool down.
If anyone has feedback on ideas on how this idea could be done better/for lore and what not, please post below.