Yes, yes, you are a Stegosaurus. Anyway, I'm gonna keep my word now since I've got time now, so lemme get started!
While Holix is a resident of piltover, he is not particularly gifted in the ways of science and invention like most of the others; however, he was born with innate fighting talent and determination. In his youth, Holix was never satisfied or content with life in Piltover. While he wasn't the brightest student, he tried to stay positive and motivated to do well in his schooling. He always finished in the bottom tier of his class, and was often on the receiving end of ridicule for his "substandard" intellect. By the time he was 17, he dropped out of school and decided to join the Demacian Military.
Military life was rough, but it wasn't anything Holix couldn't handle; in fact, he enjoyed it. During his military training, it became clear to Holix's superiors that while he wasn't bright, he sure could fight. He did so well in his training that some of the senior officers attempted to humiliate him by challenging him to a sparring match. Holix didn't feel that the challenge was fair, but he was determined that he could still win. He accepted the challenge, knowing that a loss would be more than just a bad mark on his reputation. To make it interesting, the seniors limited Holix to using only a shield, while they could each choose their weapons. He faced 3 of the seniors one after the other. Holix won without a scratch, avoiding every attack and using his shield to deflect his opponent's offense so that he could get in close and strike decisive blows. After the victory, Holix's superior officer granted him an honorary title. Holix continued to excel at his military career, fighting with only a shield, until he retired and returned home to Piltover by his 28th birthday.
After hearing about Viktor's assault on Jayce's lab and Jayce's subsequent heroics, Holix saw the opportunity to rewrite his reputation among the cityfolk. Since he didn't have an extraordinary military career, not many of Piltover's citizens knew about it and to them Holix was still "that dull kid". Holix approached Jayce with the intent of joining him in the defense of the city, and Jayce nearly laughed. After demonstrating his fighting skill in a quick sparring match, Holix convinced Jayce to let him help. Jayce agreed and started designing a weapon for Holix. Since Holix had remarkable skill with a shield, Jayce fashioned some of his arcane crystal technology into a shield. The shield allowed Holix to manipulate the arcane energies stored within, and could even recharge itself by absorbing the energy from the surroundings. While he had trouble understanding the science behind his new weapon, he quickly understood how to use it effectively. Holix then joined Jayce in the defense of Piltover to the surprise of everyone in the city, surpassing their low expectations.
Ok, so shield bearer. I can dig it. Your story makes me want to hate Jayce more than I already do, so...good job? The only issue with the lore I have is what is Holix's reason for being in the League? Can't he just be a vigilante doing work in Piltover without being at the league? Why does being in the League make him (and Jayce for that matter...) make sense?
Passive: Power Absorption - Every time Holix or one of his allied champions in a 900 range takes damage, he stores a % of the (unmitigated) damage taken in his shield (Max 90+30*level) (20% damage done to allies, 40% damage done to Holix). Power dissipates at a rate of 3% per second. Each of his auto attacks and spells will use up to a % of the maximum stored power to cause additional damage or effect.
Additionally, Holix's auto attacks are empowered, dealing 8% of his total Stored Power as bonus magic damage. (does not consume power)
Ok, so your new resource reminds me of a tank-focused version of fury. That would cover the weaknesses that fury tends to have, what with having to save up fury to do something decent and then nothing else in the fight. Also: You say a % of the power is used for Auto-Attacks, and yet it's not? Is that a mistake or am I just not understanding? Also: Is the max amount of Power static like Energy and Fury? Or does it scale like Mana? Either way, what's the max? I'm assuming 100, but I'd like to know for sure.
Cooldown: 8 seconds
Mana Cost: 30/35/40/45/50 mana
Power Cost: up to 25% Stored Power
Discharge: Holix discharges energy from his shield, dealing 40/70/100/130/160 (+25% AP) (+40% Bonus AD) (+up to 25% Stored Power) magic damage to all enemies in a 400 radius, slowing them by 30/35/40/45/50% for 2 seconds and charging enemy champions with Arcane Residue for 4 seconds. If Holix auto attacks a charged enemy, he regains 20% of the Stored Power used with this spell and consumes the debuff. While there are still enemies charged with Arcane Residue, Holix gains access to Shocker
Shocker: If Holix has 15% Stored Power, he can consume it to stun all enemies charged with Arcane Residue for 1 second.
Hmm...wait, both AD and AP ratios? Huh...Alright, seem low enough for a Q along with another ratio. It's a damn good initiate, especially if you have that Shocker able to go off. Also encourages the player to go in so that Power is regained as well...just where a tank should be going. Hmm...but to get Power back, or set off a monster stun... This is that issue of Fury I was mentioning, and also why I question what the max is. If it's 100 as I'm assuming it is, then you'd have 75 left over after a stun, and that's assuming people have been hit enough to have the max. If it does scale like mana does, then that might not be such a problem, but then that makes it so it's easy for Holix to be prepared to tank with his face. In any case...AoE slow's fine. Damage is modest. I'm just worried about the resource, as I've said.
Passive: Holix gains 1 Armor and Magic resist for every 10 points of Stored Power. Caps at 8/16/24/32/40.
Cooldown: 4 seconds
Mana Cost: 10 mana per second
Power Cost: 13% Stored Power per second (cannot be cast and maintained without Stored Power)
Holix drains the power stored in his shield to empower all units around him, granting allies 8/12/16/20/24% movement speed and healing 8/11/14/17/20 (+2% AP) (+2% Stored Power) every second, with Holix gaining double effect.
Passive caps at 40? So...at the very least a max of 400 Power...hmm... The toggle works, but 13 PERCENT per second? Yikes. Yeah, sure, it's an AoE buff and double for him, but that's gonna take away from immediate tank-ability I feel. If anything, it'd probably be used last after a teamfight is won and/or going after Baron or a tower. If that is the intent, then I guess that's fine.
E: Arcane Barrier
Cooldown: 18/16/14/12/10 seconds
Mana Cost: 70 mana
Power Cost: up to 8% stored power to cast and up to an additional 8% stored power every pulse/on reactivation and up to 16% stored power on the final pulse/on spell block
(Casts like Anivia/Karthus Wall)
Holix projects arcane energy out of his shield, forming a barrier wall at target location for up to 3 seconds. This spell will pulse up to 4 times: once upon casting and once every second after that. The first 3 pulses deal 10/20/30/40/50 (+10% AP) (+8% Stored Power) to any enemy within 50 range of the wall. The 4th pulse detonates the wall, dealing 30/50/70/90/110 (+20% AP) (+16% Stored Power) magic damage to all units within a 200 range of the wall and slowing them by 30% for 2 seconds.
Holix can recast this spell after 1 second to manually detonate the barrier, dealing 15/25/35/45/55 (+10% AP) (+8% Stored Power) magic damage and slowing all units in a 200 range of the wall by 30% for 2 seconds.
Additionally, if any skillshots hit the barrier, the barrier stops the spell and deals 30/50/70/90/110 (+20% AP) (+16% Stored Power) magic damage to the caster and slows them by 30% for 2 seconds. Skillshots that would normally pass through objects are destroyed. Skillshots with detonating effects are detonated on collision. Blocks 1 spell before dissipating.
I like the concept of the wall that blows up to slow and blocks ranged skills. Thing is I'm worried about ults. Like I'm assuming this would completely block Ashe's Enchanted Crystal Arrow and Ezreal's Trueshot Barrage, but of ones that don't really have like...I guess you could say substance to them? Say for example Lux's Finales Funkeln or Sona's Crescendo? Hell, what about Caitlyn's Ace in the Hole, which is blockable by champions? Like I said, the slow and the minor magic damage is just fine. I'm just worried about the ability to just shut down an ultimate.
R: Meteor Strike
AoE Diameter: 800
Mana Cost: 100/125/150 mana
Power Cost: up to 50% Stored Power
Holix utilizes a burst of arcane energy to propel himself into the air, becoming untargetable then landing at target area after up to 1.5 seconds depending on the cast distance (0.5 sec minimum). The impact deals 150/225/300 (+40% AP) (+50% Stored Power) magic damage to all enemies, knocking them back 200 units and slowing them by 20% (+1% per 2 Stored Power used on this spell) for 3 seconds. For 6/8/10 seconds after landing, Holix generates 10% of his maximum Stored Power per second, preventing the passive % decay for the duration.
BUA! 50% power...Let's see what this does...OH! Power generation, alright. While the damage is impressive for a tank, Meteor Strike makes for a damn good initiate. Especially with combination into other skills, such as Discharge into Shocker. I like this a lot, has the feeling of an ultimate. I'm really not sure what I can say to make this any better. And don't worry, it's different enough from Grand Skyfall I'd say, especially with the CC this has and the Power mechanic.