Simply put, comment a concept and I'll reply with a kit, abilities, and maybe a lore (lore is kind of hard atm because of Riot's retcon). It would also be helpful if you would add what role you want the concept to fill: Support Marksman/ADC Mage/APC Fighter/Bruiser Tank Assassin
Jungle is a position, not a role; unless you're 
- but if you'd like a champion to fare well in the jungle I will accommodate you.
If you want to add additional details for me, go for it.
GroundRuleDouble1 votesWater mage. Think Posidon. Can control water, create water from air, and can create water elementals (pets).
SociopathFriend2 votesWater mage eh? Might have to tinker around a little but-
Innate: Living Water Champion X is comprised of water, and so takes 5 (+10% AP) less damage from single target attacks and spells from enemy champions.
Q: Torrent A raging torrent of water falls onto the target area, damaging and slowing all units in the AoE for several seconds.
W: Tempest After a brief delay, water will explode upwards at target location; knocking up any enemy in the area.
E: Surge Champion X flows to target location, ignores unit collision but cannot go through walls. Upon arrival, he bursts upwards; gaining a shield if he strikes an enemy champion.
R: Ruler of the Seas Champion X unleashes a massive circle of aquatic magic around himself. If an enemy champion remains in the area for too long, a sea serpent will rise up and root them, dealing damage.
Overview I'm picturing a sort of sustained-combat mage- like Lux for example. He can play hit and run until he lands his Tempest and then he Surges in to deal damage while the enemy tries to get away. A very all-or-nothing champion. His passive enables him to become moderately tanky by just building AP, but he has no sustain options and his regen is likely to be horrible to compensate.
Lore I'm gonna say he's a relative of Nami; maybe a brother, eager to find his lost sister- maybe a father searching for his child- or perhaps a villain, seeking to demonstrate his power and assume undisputed rule over the seas of Runeterra.
GroundRuleDouble1 votesI would love to play this guy. Seems like he could be an assassin. Depending on the ranges:
E to get close. W, R (R starts before W knocks up), Q to slow to keep them in range of R.
Full AP build would be great. Deal all this damage while taking 50-70 reduced damage from attacks and spells?? Insane! Where do I sign up?
SociopathFriend1 votesBear in mind, any numbers would be tentative since I don't have the luxury of testing; that probably would need tweaked- the number was just an example of the idea.
Sinneli1 votesSort of a pied piper. Summon creeps/upgrade minions into creatures which follows them around/constantly attacks one person they target. Can either be bruiser or tank maybe?
SociopathFriend1 votesHmmm, a minion champion eh? Let's see here... not sure 'Tank' will work and still be healthy so we'll go for more of a bruiser.
Innate: Song of Servitude Champion X can choose a minion from one of his waves. This will create a copy of that minion that will follow him around; he cannot select a Super Minion. This minion will have the same stats as other minions spawned at that time and will not increase. It will not receive Baron Buff or Banner of Command. If the minion is killed this ability has a 30 second static cooldown and will give double the gold of a regular minion. This minion will not regen but will use on-hit effects of items. Sheen procs will only work on Champion X auto-attacks.
Q: "Attack, my slave!" Champion X deals damage to the target and marks them, ordering his minion to attack. The minion will deal additional damage to the marked target based on AP for the duration of the mark.
W: "Servant, to me!" Passive: Champion X's minion will gain MS when moving towards an enemy that Champion X is attacking. Active: Champion X calls his minion back to him, this places a defensive steroid on the minion that gives it a shield that scales based on the bonus health Champion X builds.
E: "Hold them for your master!" Champion X commands the minion to slow the targeted enemy. If the enemy is marked with "Attack" they will instead be stunned for a short duration.
R: "Minion, unleash your power!" Character X buffs his minion; transforming it into- we'll call it Spawn- for a short duration. All of the abilities will still function as normal- though reactivating the ultimate will have Champion X "Consume" Spawn to regain health equal to the health Spawn has remaining. (Short range) Spawn will grow into his own model that is fairly large (about Super Minion size). Spawn will gain a portion of the bonus stats Champion X has and will gain access to all item effects instead of just the on-hit ones (Thornmail, Sunfire, Frozen Heart etc). Spawn will slow all nearby enemies in the radius of his transformation.
Overview Champion X is meant to be very reliant on his minion, ensuring that he takes proper care in using it as without it he will be very weak. He creates a copy of a minion instead of just taking one from the wave as that would leave his enemy lane down a CS without a fight. The minion will not increase in power on its own; but letting it die leaves him without a better half for 30 seconds so he must be careful in how and when he disposes of it. Champion X will likely have very low base stats to help offset bringing an extra minion to his lane. To encourage him to not be taken as a Support, he can self-cast his abilities and can target his minion, but not allied champions.
Lore I don't have a proper lore, but I can see his as sort of a power-hungry sadist that enslaves others to do his will.
showcase251 votesI just have to shout this out:
This is so amazing. Someone else recently had posted a Pied Piper type champion. Just anpther way to look at this concept.
SociopathFriend1 votesIf you stick around long enough- you notice a pattern in the concepts people use. I can't count the number of times people have asked Riot for a Monster Tamer Champion.
showcase251 votesNot new to League, but really new to the Boards.
I'm going to take the cowards way out and say:
Great Minds Think Alike.
__
Tamur1 votesMaster of Unarmed Combat
Role jungler
SociopathFriend2 votesHmm, 
and 
are both pretty much that exact niche; you could possibly count 
too... but, I'm a man of my word.
Innate: Focused Fury Champion X uses his anger to empower his attacks; every auto-attack will mark his target up to a maximum of 3 times. Using an ability to damage the target will heal Champion X for so much per consumed mark.
Q: Striking Technique Champion X strikes his target, if the target is killed the ability is immediately brought back off cooldown.
W: Speed Technique Champion X leaves a clone at his starting location and goes into stealth as he dashes behind his enemy, gaining increased damage against them for a short duration IF he completes the dash. The dash is not instant and can be interrupted by any CC besides a slow or blind- negating the damage boost.
E: Blocking Technique Champion X fires a skillshot at the enemy, sealing their abilities (silence) for several seconds.
R: Final Technique Champion X channels briefly at target location before punching the ground, causing a shockwave to knock-up and deal damage to all enemies in range.
Tamur1 votesInteresting
SociopathFriend1 votesI think I got overly hung-up on the whole 'technique' thing.
Tamur1 votesnot really I think you hit the mark really.
showcase251 votesLet's really work out that creative muscle:
Role: Support
Champion Type: Wild Life Big Game Trapper (AKA Exotic Animal Collector who shows them off alive).
SociopathFriend1 votesEveryone has a crush on :p
Support Hunter eh? I've got just the thing:
Innate: AP rounds Every time Champion X damages an enemy with an auto-attack, it removes 1% of their armor for 3 seconds. This effect will stack up to 5 times; it will increase to 2% at level 7 and 3% at level 14.
Q: Tranq Dart Champion X tranquilizes the enemy, reducing their AS and MS for a short duration.
W: Harpoon Champion X lays down a Harpoon trap. If an enemy walks within 300 range the trap will activate, dealing damage and causing them to be restricted to the 300 radius from the trap until the trap takes damage to be destroyed.
E: Hunter Sense When Champion X stands still for 2 seconds, he gains true vision of all units in range; this ability will not reveal wards, shaco boxes, or teemo shrooms.
R: Collection Champion X raises a barrier around themselves, enemy and ally units will not be able to bypass the barrier unless it is broken- the barrier's health will scale with Champion X's bonus health.
showcase251 votesThank you. I like where you went with that.
I guess Was a gimme, lol
SociopathFriend1 votesOh by the way, anyone can use the kits however they want- I don't need credit.
Tamur1 votesYou still doing this?