????, The Shapeshifter
For starters I'm not sure if someone has already posted this idea, I don't visit the Board Discussion pages. Now here's the main idea, imagine a champion who is pitch black but kind of like a static pitch black that makes him look like a glitch. He doesn't have any features besides I giant creepy smile.
His skills is where it gets interesting, he doesn't have any. The way he gets his skills is that he steals them from other champions. If Teemo hits him with his blind dart and he presses Q within 1 or 2 seconds he can steal the skill and he is stuck with it for the rest of the game. This makes his skill set based entirely on the enemy team, but to prevent someone from having 4 ultimates you can only copy one Q, one W, one E, and one R.
His base stats are slightly above average with decent well rounded health, mana, Attack, and so on. This is to prevent people from getting destroyed in the beginning because of the lack of having their own skills but the growth rates should be slow to prevent the stats from becoming op.
This idea is kind of rough and crude, I don't have any lore or a good name yet and I can't express everything I'm thinking correctly, so I left some information out, but let me know what you guys think!