Cii, the Monster of the Sewers
I want to set out and make a Splatoon-like champion concept, because that game is super fun so let's take a page from a fun game and implement it to another fun game with adjustments to make it work out.
Cii [see] was a vastaya girl, but after a trip to Zaun and some experimentation from mad scientists she transformed from being a bird-like creature with a fox tail to more of some kind of amphibian creature which keeps her fluffy fox-like tail. Whenever Cii is surrounded by a lot moisture, whether it be moist air, water, or even sludge, then she transforms into this new monstrosity being able swim through it at extreme speeds!
(Imagine something along the lines of human-to-hulk, instead of anger for the transformation it is just simply moisture that triggers it.)
Cii is a roaming mage, she can be played mid lane, but her core position will be as the team's jungler to really utilize her mobility! She has low burst and low range, but it is made up with her very high mobility and other utility, she is a real play making champion (at the cost of being risky most of the time; high-risk, high-reward)!
Attack Range: 450 units [kind of like a hand cannon, but spits out sludge] Attack Speed: 0.690 +4% per level Movement: 340 units per second Sludge Pool: 100 +10% bonus mana Sludge Regen: 10 Sludge per second increased by same % of base mana regen (i.e. 100% base mana regen = 20 total Sludge per second)
[UNIQUE ELEMENT: Blue buff will buff up Sludge regen massively since Sludge is being treated as an unique mana-like resource (blue buff effects energy regen as well).]
[OTHER UNIQUE ELEMENTS: Items like Morellos will restore 40% Sludge on kill/assist; items like Archangel's Staff will grant ability power equal to 30% Sludge since your maximum pool size is that much smaller over mana (you will get about the same AP as mana users this way).]
Sludge Swim (Passive): Cii's attacks and abilities leave behind sludge as they travel for the next 60 seconds.
If Cii is on sludge she transforms into her monster form granting her 10% increased total movement speed and ignore unit collision, increasing to 100% while out of combat for 5 seconds.
Cii's abilities consume Sludge. The maximum amount of Sludge held can be increased slightly with bonus mana and Sludge regeneration increases with % base mana regeneration. Cii restores Sludge while swimming in sludge.
S. Bomb / S. Jump (Q): Cooldown: 4 seconds; Cost: 20/22/24/26/28 Sludge; Range: 600 units Passive: Cii's basic attacks against monsters reduce this cooldown by 2 seconds on-hit.
Active: Cii fires a ball of sludge to the target location exploding on impact [400 unit radius] dealing 80/110/140/170/200(+70%AP) magic damage to enemies it passes through.
Monster Form: If Cii is already in sludge then she jumps to the target location, dealing the same damage to enemies she passes through. Jumping through minions and monsters stuns them for 1.25 seconds.
Goo Blast (W): Cooldown: 16/14/12/10/8 seconds; Cost: 40 Sludge; Range: 800 units Cii blasts a giant glob of sludge in the target direction dealing 100/120/140/160/180(+40%AP) magic damage and pushing enemies along its path.
Monster Strike (E): Cooldown: 10/9/8/7/6 seconds; Cost: 35 Sludge; Range: 600 + 300 units Passive: Cii's in-combat swim speed is increased to 12/14/16/18/20% total movement speed.
Monster Form: If Cii is already in sludge then she swims at an extreme speed to the target enemy and beyond, dealing 5/5.5/6/6.5/7%(+2% per 100AP) of the target's maximum as magic damage (max 400 vs monsters) and stunning it for 1 second.
Terror of Filth (R): Cooldown: 130/100/70 seconds; Cost: 40 Sludge; Range: 600 units Monster Cast One: If Cii is already in sludge then her movement speed is set at 900 units per second, but she cannot exit sludge for the next 6 seconds.
Monster Cast Two: Cii jumps into the air bringing up an eruption of sludge knocking up struck enemies for 1.25/1.5/1.75 seconds and dealing 150/200/250(+60%AP) magic damage.
UPDATE:
S. Jump:
No longer requires Cii to jump into sludge to create a more fluid gameplay, but still requires for her to be in monster form (two different versions of the same ability based on whether she is in sludge or not)
Minion and monster stun duration increased to 1.25 seconds from 1 second; this and the auto soft reset against monsters is to help her jungle without giving her shields or heals. The spammy Q nature, especially in the jungle, is at the cost of depleting your Sludge very fast and has a very reliance on blue buff for the fast clears - similar to Olaf's clear speed.