Crass: Targon's Warden : A champion kit concept
Global/roaming/control support concept.
Too lazy to write a full story and intro but here is a full kit and I'd like your thoughts!
Passive Unyielding spirit: Gain tenacity and a cooldown on spells based on %missing health Gains .3% tenacity per 1% missing health Gains 1/2/3 seconds off cooldowns when beneath 75/50/25% HP (percent CDR is applied after this reduction)
Q: Tremors 60/65/70/75/80 Mana :: 800 Range :: 15/14/13/12/11 second CD Periodic knockbacks towards your character in the center of the area in a line perpendicular to character, lasts 3 seconds, deals 25/40/55/70 + (40% AP) damage per tremor, tremors 3 times at .5-1.5-2.5 seconds into the duration, slows 20% + (10% AP) AoE 400 width/200 length Knockup AoE width 400/50 length
W: Flux bloom 40 Mana :: 600 Range :: 30 second CD Place a seed at target location, grows over time and grants bonuses depending on it's growth Growth takes 10 seconds and is affected by cooldown reduction and your passive. Stage 1: Seed - Acts like the mandrake ward - alerts you when an enemy walks within 500 range of it. Stage 2: Shoot - Grants vision, visible, becomes targetable, 1 HP Stage 3: Bud - If in brush becomes invisible, 2 HP Stage 4: Bloom - Grants bonus 1/1.5/2/2.5/3 + (3% AP per second) (1000 range) and move speed (10% AP) (400 range) to allies near it , 3 HP Stage 5: Brush - If untouched up to this point, it becomes brush (size of river brush) which your team will always have vision of but no longer provides vision around it. If connected to an existing brush you also gain vision in that brush. Pink wards and sweepers and any true sight abilities will reveal the bush and render it destructible. Lasts 2 mins, grants vision within 800 range while in stages 2-4, maximum seeds 4/6/8/10/12
E: Landslide 100 Mana :: 350 - 700 Range :: 15 second CC Vector targeted 'thresh flay' that quickly drags targets the whole way. Deals 80/110/140/170/200 + (70% AP) .7 second delay before the drag, drag lasts up to 1 second.
R: Boundless life 100/130/160 Mana :: 160/140/120 second CD
Slams ground at self location dealing 100/250/400 + (30% AP) damage and roots enemies within 500 units for 2 seconds. Then channels for 1.5 seconds before blooms burst dealing 100/200/300 + (25% AP) damage and also knocking enemies back 300 units. Enemies hit by more than one bloom take 30% reduced damage from other bloom explosions and aren't knocked back again. Blooms rapidly explode in order of distance from Crass. Can place 1/2/5 extra blooms while channeling ult
Example build: 
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Thoughts: A very control focussed mage support. I know we're all a little tired of the domination of tank supports. The only reason lulu fits into team comps these days is that she provides a lot of control on relatively short cooldowns. This shuts downs assassins and bursty fighters but also often removes the influence of strong frontline champions too.
The thoughts behind Crass are that he's very good at controlling space and positioning of the enemy team whilst also providing his own team with more options and more information wherever he goes.
Not gonna lie, the passive was created to deter people from building a tank build. As a tank he'd be really oppressive in a bad way and the way that the passive is set up it makes it really hard for a tank to fully utilise it. Staying totally healthy is a problem for Crass so Crass thrives in the middle of battle, taking ambient AoE damage using his reduced cooldowns and tenacity to strafe in and out of the fight whilst regenerating due to preemptive seed placements.
IF this passive is still strong with tanks an alternative could be an auto attack buff. -Auto attacks slow enemies struck by (3% AP). The slow affect increases in size scaling with AP - slow AoE = 35% AP This passive is useless late game without roughly 400 AP.
Q is a simple zoning tool. Applies a decent slow and knocks back along a line in the middle. Dashes and blinks can get past it but walking through is almost impossible.
W is a strong ability for Crass, freeing him from the need of a sightstone but replacing it with a riskier one with higher rewards. The ability is actually quite strong and I'd like your opinions on it. Healing and movespeed auras dont's stack. In lane it provides a lot of safety and allows crass to roam faster and further with each additional seed he plants. Perhaps he should not be allowed to use sight wards or the sight trinket or maybe seed growth would trigger a mana cost requiring better resource management.
E is another very strong skill. Intentional and free displacement of enemy champions is a rare ability in LoL (Condemn, Gragus ult, Voli flip, scatter the weak etc). Also the only reliably strong damaging ability. I'd just describe it as a thresh flay on steroids. Great against juggernauts, weak against assassins.
R only anti assassin spell in your arsenal really. Primary uses are to save yourself or allies near you and to set up kills in other lanes with the seed burst knock back.
Other roles? I'm certain that jungling and laning are possible for crass. The E - Q - R combo would be a devastating amount of burst with a seed added from the ult and a good set up for wombos. E and Q would be good for kiting out monsters too.