Thought I'd combine my love for BioShock with LoL: presenting Booker DeWitt, the False Shepherd himself. Obviously, take this champion kit with a grain of salt (or rather, a grain of Salts :P).
Veni! Vidi! Vigor!
Booker can purchase permanent additional effects to his abilities at the item shop. Each passive or basic ability upgrade costs 500 gold, and Undertow's upgrades cost 1000 gold, though they can only be purchased after upgrading every other ability.
One of the core gameplay themes in every BioShock game is customizability: literally everything about you can be upgraded and reconfigured to suit your preferences. You can play any game in the series twice, and end up with a completely different set of abilities and specializations. By contrast, League of Legends champions have much more fixed kits, since having the same champion just swap out kits entirely would dilute their concept (why not just make more than one champion instead?). While this overall concept is not meant to be a serious addition to the League roster, I think there can be a happy middle ground between those two extremes, in which a champion could start out with a baseline kit and have configurable upgrades to enhance it, in a manner similar to Viktor's and Kha'Zix's but with a bit more variance.
Overall, I want Booker to have the same overall role: he's a fighter loaded with crowd control, with a significant tradeoff between reliability and power on each of his abilities, which he has to charge (every Vigor, or superpower, in BioShock Infinite can be charged). Though he has a lot of CC and a fair bit of damage overall, he heavily telegraphs all of his abilities, and has to telegraph them even more if he wants to reach their full power. The customization mostly boils down to whether Booker wants to directly strengthen his abilities -- to provide stronger crowd control or additional utility, for example -- or broaden them to affect more targets.
Health for Salts
Booker can sacrifice his health to cast spells if he does not have enough mana, at a rate of 2 health per 1 mana required. At 1 health, this effect is disabled.
In the BioShock franchise, access to superpowers (Plasmids in the first two, Vigors in Infinite) is tightly gated by a resource (Eve or Salts, depending on the universe), and so I think it would make sense to tightly gate Booker's powerful abilities through mana, which I deliberately stunted so that he would have a hard time regenerating it naturally, and coupled to high mana costs. Health for Salts would work as the nuclear solution to eliminating Booker's mana problems by essentially tying his health bar to his mana bar, meaning he'll only run out of mana upon dying. Obviously, burning through mana would take a toll on Booker's health, and so he'd still have to manage his mana, but would be able to mitigate the cost through health and health regeneration, in addition to mana. Overall, this would be the better option if you were deciding to build Booker more like a tank, as you'd be building a lot of health and mana.
Blood to Salt
Booker restores 1% of his missing mana every time he takes down an enemy.
Whereas Health for Salts is more of an immediate, tank-oriented solution to Booker's mana management, Blood to Salt is meant to offer safer, yet slightly slower mana regeneration, by allowing a more damage- or support-oriented Booker to regenerate mana as he clears waves or lands kills and assists against champions. It's for this reason that I'm having the bonus activate upon participating in a unit's death and not just killing them outright: I think a support Booker playstyle could exist (he has the CC, peel and utility for it), and in doing so he could have this minigame where, on top of executing minions with Relic Shield and its upgrades, he could also lightly damage them before letting his marksman get the last hit, in order for both of them to reap some kind of reward.
RANGE: 425 - 1000
COST: 60 / 70 / 80 / 90 / 100 mana
COOLDOWN: 18 / 16 / 14 / 12 / 10
First Cast:Bookerchannels, increasing Charge's damage and slow over 2 seconds.
While channeling, Booker is immobile, and cannot attack or use his other abilities. After 4 seconds, Charge is cancelled, goes on full cooldown and refunds half its mana cost.
Second Cast:Bookerdashes in the target direction, dealing physical damage to all enemies he passes through and slowing them for a duration equal to the time spent channeling, up to 2 seconds. Booker stops upon hitting an enemy champion, applying on-hit effects.
Due to how most of BioShock's more refined combos come from using melee attacks (and likely from personal preference), I decided to make Booker melee, and balance him around that: he has reach through his spells, but that reach is never instant. In order to move around in-between spellcasts, I think it would make sense to give him Charge, the mobility power in BioShock Infinite that also happens to be tied to Booker's melee weapon, the Sky-Hook. It applies on-hit effects for a number of reasons: first off, Booker's going to be spending a lot of time not actually attacking, even at melee range, and this would let him put his life steal to good use, especially if charged for long enough, whereupon it would provide healing equivalent to that you'd get from an Infinity Edge-enhanced critical strike. The second, and most important reason, is that I want to implement one of the most iconic BioShock combos, the one-two punch, where electrifying an enemy (using Booker's E, Shock Jockey) causes them to take massive damage from the next attack used against them. Being able to do so using Charge would provide a huge amount of burst and give Booker extremely potent initiation on squishy targets.
This is the direct enhancement version for Charge, intended to most benefit a squishier, more damage-oriented Booker. A tanky Booker could initiate better with this, but would also be able to handle abilities thrown at him, whereas a damage-dealing Booker could be use this for hit-and-run entries and exits when trying to pick off single targets.
Enemies near the initial target take half of the charge's damage and are slowed for the same duration, but at half the strength.
This is the AoE addition for Charge, which I think would be more suited for a tanky Booker, despite mostly propagating damage. It would sort of turn Charge into a soft Malphite ult, with most of the crowd control focused on a single target.
Return to Sender
RANGE:850 / 175
COST: 70 / 75 / 80 / 85 / 90 mana
First Cast:Booker creates a barrier in front of him that absorbs all incoming enemy projectiles, storing their damage up to a threshold. While the barrier is up, Booker cannot use his other abilities.
As a generally slow-moving melee champion who has to continuously expose himself while casting spells, I figure he could use Return to Sender, a Vigor that, in BioShock Infinite, is used to create shields and collect the enemy's bullets before firing the resulting ball of molten metal back at them. I think the concept could work here: although the creative space for projectile absorption is getting pretty cramped, here I think there would be a good enough mechanic to have another. A common complaint for Wind Wall is that there's no way to "break" it, and while implementing that wouldn't really work for the ability itself, I think it would be possible to implement an upper limit to the projectiles one could block here. Overall, I think the ability would work well as reverse-poke, as well as in-fight protection.
While active, the barrier encompasses Booker completely.
Sender Aid is the AoE enhancement for Return to Sender, one I think would be better suited for when he's in the middle of fights. It would also help if Booker's trying to make safer escapes, as he'd otherwise be unable to escape and protect himself at the same time.
Send for Less
Booker restores mana equal to 50% of the damage absorbed.
Send for Less is the direct enhancement for Return to Sender, which would play more into the ability's counter-poke playstyle. On top of helping with Booker's mana issues, it would also allow him to act from a distance with much more freedom.
COST: 60 / 65 / 70 / 75 / 80 mana
COOLDOWN: 20 / 19 / 18 / 17 / 16
First Cast:Booker charges for up to 4 seconds, producing electrified crystals. Booker starts with one crystal, and gains another for every second spent charging up to a maximum of 5. While charging, Booker cannot use his other abilities.
Second Cast:Booker releases the crystals at the target location which, upon touching the ground, activate after a 0.25-second delay. Enemies who step on a crystal consume it, take magic damage and are stunned for 1 second, during which the next champion basic attack against them will deal bonus magic damage. Crystals last up to 3 seconds, and enemies who consume a crystal cannot activate any others.
Spell shields will block the damage and effects, and activate the immunity.
Whereas Charge is the most offensive of Booker's basic abilities, and Return to Sender the most defensive, Shock Jockey covers the middle ground, allowing Booker to set traps or, when quick-casted, try to shock individual enemies near-instantly. A core part of this ability is the One-Two Punch, which in the BioShock games causes shocked enemies to take massive damage from the player's next attack, and I think it's worth implementing here (you get a pseudo-crit on your next attack if you're quick enough). Not only would this synergize with Charge, but its universal activation would allow a support-ish Booker to set targets up for massive damage from the marksman, and generally mark targets for death from mid-ranges.
Shock Chain Aid
Shocked victims will also shock the nearest nearby enemy, applying the exact same effects.
Spell shields will block the damage and effects, and activate the immunity.
This is the AoE-oriented upgrade for Shock Jockey, and one I think more oriented towards quick-casting (you'd need less crystals to catch multiple enemies, and so would have to charge less). Overall, this would benefit a tanky Booker more, I think, as it would allow for quicker multi-target CC.
Shock Duration Aid
Shocked enemies are stunned for an additional 0.5 seconds.
This is the direct enhancement for Shock Jockey, one I think would work best for a damage-oriented Booker (you'd get to disable enemies for longer, and would have a longer window of opportunity to One-Two Punch them). You could also pick them as a tanky Booker for even greater crowd control, but it's likely you'd want more immediately available crowd control then.
RANGE:125 - 1000 / 75 / 500 / 175
COST: 100 mana
COOLDOWN: 90 / 75 / 60
First Cast:Booker channels and sends out a tendril of water that extends its range over 2 seconds, pushing aside enemies it passes through.
While channeling, Booker is immobile and cannot attack or use his other abilities. After charging for over 4 seconds, Undertow is canceled, going on full cooldown and refunding half its mana cost.
Second Cast:Booker retracts the tentacle, pulling in the first enemy champion caught near its tip, bringing them directly in front of Booker's location and suspending them for 2 seconds. While the target is suspended, Booker can select one of his basic abilities to use on them, dealing physical damage and applying a unique effect:
Charge: knocks the target back, causing them to stop at the first enemy hit, deal the same physical damage in an area and stun all affected enemies for 1 second.
Return to Sender: Booker gains a shield lasting up to 4 seconds equal to double the physical damage.
Shock Jockey: Booker deals bonus magic damage equal to 30% (+ 2% per 100 AP)of the target's missing health.
In BioShock Infinite, Undertow is a Vigor used to either push enemies back or suspend them in the air for Booker to combo off of them, and I think it would be the perfect ultimate here for its interaction with the rest of Booker's kit. The format's sort of like the scrapped version of Vi's ultimate, where she got to perform three different kinds of punches on her target, though here I think the suspension itself is a good enough setup for special combos, where Booker could either punt his enemy, shield off of them or try to execute them. These three options should be available even if the related basic abilities are on cooldown, and shouldn't incur a cooldown either (the effects are separate from the actual abilities).
Undertow can pull up to two enemy champions at a time.
This is the direct enhancement to Undertow, and one I think would help in anti-poke comps, as the massive range boost would allow Booker to pull even a Xerath firing from his own team's back line if used well.