Champion Concept: Isaac--The Supreme Huntsman
Basic Concept My idea for Isaac is that he's a human hunter who's debatably the best at what he does. Unlike Rengar, Isaac doesn't hunt for the sport of it, and unlike Vayne, he doesn't hunt to rid the world of evil. Isaac hunts because it's the best way for him to make a living; he never makes a kill for no reason. Most of the time, Isaac hunts common game animals and sells the spoils of the hunt (meat, fur, etc.); on occasion, though, he'll be hired to take down or capture a monster. He's even been known to put his skills to use tracking down and capturing criminals. Isaac doesn't see the point of going after large and dangerous prey without good reason (he's been hired to kill it, self-defense, etc.). However, if he found himself in a situation where innocent lives are being threatened by a monster, he wouldn't just leave them high and dry. His weapon is a Hextech Rifle.
Relations with other Champions Rengar, Teemo, and Vayne respect his hunting prowess and knowledge of the wild. Rengar sees Isaac as something of a rival (the feeling isn't mutual, because Isaac doesn't really care about other hunters as long as he gets paid), while Vayne is somewhat disappointed in him, thinking he's wasting his considerable skill that could be put to use fighting evil. Ahri, Maokai, and Udyr aren't his biggest fans, but aren't full-out against him due to the fact that he doesn't kill needlessly.
Champion Kit Passive--Tracker: Isaac is adept at seeing the trails left by all manner of creatures. Where enemy champions walk, they leave a trail that disappears after a short time (time the trail lasts increases with Isaac's Level and ranks in his Ult). This trail is visible to teammates, but only when it is actually within Isaac's Line of Sight. He has no way of knowing which champion left the trail, and he has to rely on which direction the trail is decaying to be able to determine the direction the champion moved. I'm thinking the trail should be segmented and colour-coded by how old the segment is (red for 1-second-old trail, orange for 2-second-old trail, etc.) Q--Sustenance Hunting: While not on cooldown, Isaac will gain a stack of Game every time he kills a minion or monster (increased for Monsters, increased further for Large Monsters), up to a maximum amount of Game stored (this amount increases with ranks in this ability). Stacks will disappear after a short period if no new stacks gained (if at max. stacks, killing a minion or monster will refresh the timer even though no stacks are gained). When this ability is activated, Isaac consumes all stacks of Game to heal himself an amount per stack (scales with AP). Upon entering the store, all stacks of Game are sold for 5 gold each (does not activate when opening the store while unable to purchase). W--Steadied Shot: While toggled on, Isaac drops to one knee to steady his aim. Roots self but gives additional attack range and damage (bonus damage multiplies appropriately with crits). There is a short channel time to toggle off. E--Trap Line: First cast starts laying a trap at the location selected. After a short time or after a second cast, stops laying trap and starts camouflaging it. A third cast will cancel camouflaging; if camouflaging is allowed to complete, the trap will be stealthed. When laid, the first enemy to walk over trap is damaged and snared. The longer the time spent laying the trap, the higher the damage and snare time (up to a cap); rate of increase while laying scales with ranks in this ability. Traps will disarm themselves after some time. R--The Hunt is On: While active, increases potency of passive and abilities in the following ways: Length of time on trails left by Tracker is increased. Collect double Game while Sustenance Hunting is not on cooldown, and can still collect normal Game while it is on cooldown. Instead of rooting, Steadied Shot greatly reduces Movement Speed. Take reduced time to lay and camouflage traps.
In-Game Role I see Isaac being strongest as a Squishy Ranged Assassin Jungler. His Passive is best put to use between lanes, where he can give allies a head's-up on incoming ganks. While his Q can be used well in Top Lane or as ADC, it's most effective in Jungle, where it offers great sustain or, if the extra sustain is unneeded, can give him enough bonus gold that he's not as set back by executing a gank. His W is best used when he can expect either to finish off the enemy quickly or to have the enemies heavily peeled. The relatively long cast time on his E means it's best used in an area that enemies aren't currently but can be expected to go (Dragon, Tri-bush, etc.) or as extra vision to reduce the need for wards.