[Champion Concept] Gef'thar, Dolour of the Abyss (health-based support)

Disclaimer: all names and numbers are flexible - is it all about concept and mechanics.

So we begin:

Gef'thar, Dolour of the Abyss

Lore: The lifes and worlds consumed by the Void are not simply destroyed. Captured in perpetual agony, they fuel the Void on its path to oblivion. But whenever something burns, ashes remains. Over the millenia the leftovers of these poor entities were gathering in the blackest abyss. With recent victims of the Void becoming the inhabitants of Runeterra, irradiated by unstable magic, these remnants gained form in the wild outburst of will. Gef'thar, Dolour of the Abyss was born, the collective of countless martyrs, determined to use the last spark of theirs volition to destroy or at least stop the Void in its endless feast.

Apperance: Something like Koven from Super Metroid
http://www.metroid-database.com/bestiary/artwork/joe_koben_sm.png

Or Dark Star from Slayers
http://img1.wikia.nocookie.net/__cb20051017025558/kanzaka/images/5/55/Darkstar.jpg

So basically "The Legion" Champion. Maybe pushing the depressive violent torment trope little too far for LoL, even further than Tresh/Urgot.

Now, the Kit. Gef'thar is a tanky support that utilize his own health to cast abilities, filling the niche of the symbiont/parrasite unit (in bonduaries of LoL gameplay, so not causing "troll" situations for allies or too frustrating moments for enemies).

Passive: Hatred

Every time Gef'thar takes damage, he send a wave of hate around him (range 300-350) that deals magic dmg equal to 10-15% of damage taken (before reduction).

His main damage skill. It promotes being in the middle of the fight on enemies faces, and actions taken to remove Gef'thar from allies face can be very painful for them.

Q: Voidleech
Cost 8% current health.

Linear skillshot dash with 0.5s cast time. Stop on first enemy unit hit dealing initial AD dmg, stunning it for 1s and slowing by % for 2s after stun wears off.
If unit is an enemy champion, Gef'thar fasten to him for 2s. Gef'thar is dealing % of max HP magical dmg per half-second, is considered channeling, can be interrupted and move togheter with enemy champion.
Gef'thar heals himself for a 30% of damage dealt.

Potent but telegraphed dash + CC. Nice damage but for at least 1 second you are at mercy of enemy that can walk/flash/dash/lantern towards his tower/teammates.

W: Reprieve

Passive: Gef'thar gains 20/40/60/80/100% increase in total health regeneration.
Active: Gef'thar tether to targeted ally champion, giving him 15% of his MS and 150% of his health regeneration (so Gef'thar have -15% MS and -50% HP5).
8 second CD, tether range 1k.

"Symbiosis" skill that allows him to help allies but at cost of his own capabilities. Infuse-type healing.

E: Phase Out / Phase In
Cost 5% of current health.
Second cast after a minimum 1 second.

Gef'thar phase out to the Void pulling towards him all nearby enemies and getting bonus Armor and MR (or just %DR) for up to 4s. When this effect ends or after reactivating, Gef'thar phase in to the real world dropping bonus resistances and knocking all nearby enemies back.

His tanking skill with medium duration. Some CC tied with dimensions manipulation.

R: Mindkiller
Costs 2% current health per half-second.
AoE radius - 500.

Gef'thar penetrates minds of nearby enemies dealing small amount of true damage to them each half second. Every time unit takes damage from Mindkiller, it receives a stack of Braindead for 3s, max 10 stacks. When Gef'thar ends Mindkiller, all units affected by Braindead are feared for 0.15/0.20/0.25s for each stack.

*Fundamentally this is delayed AoE CC. It has potential of being team-wide 2.5s fear, but it takes 5 seconds and good positioning to reach that. On the other hand it is elastic - "Ok, I need this fear NOW even if it is non-maximal". Even after enemy leaves the range, you still have 3 seconds to decide when to CC him. *

Summary: So we have manaless support with heavy CC, sustained damage and some health sustain/utility for allies, but he lacks in mobility - he has only one delayed dash blocked by minions and even self-slow.
While he have means of engaging, he lacks good "leave me alone / get out of jail" skill.
As every tank he needs a post-combo presence in fights - Gef'thar have his DoT ultimate with stacking CC, continuous speedbuff/heal for MVP and his passive that can deal nice damage even with just ambient AoE hitting him.

Build: Targon Line + Warmog + Rylai (slow on ulti/passive).
Aegis/BV for nice regen and MR. (With BV in-battle regen and rank 5 of his W, Gef'thar gives W-target additional 135 HP5.)

I would greatly appreciate a constructive feedback, especially if health-based (manaless) support is even a balanceable idea, 'cause I know that my concepts have many rough points but I think we can work it all out togheter :)

If someone is interested, here are links to my previous works - Harpy, The Heavens Vengance; Banshee, Undead Princess and Erik The Great.