He is an AD Assassin that depends purely on critical strikes with Instinct as a resource. Instinct points grant instant criticals, each consumed by basic attacks, and can only be gained from his ultimate. They do not expire over time neither when the attack misses, or when the critical chance is already 100%.
Because of his stalking mechanic, El'ramir thrives in teams with good teamfights because after going in and throwing Vehement Shreds, he can rely on his ultimate to keep himself alive and Shadowcharge to stick to his targets, killing them usually before the effect ends.
El’ramir’s critical damage modifiers are applied before Infinity Edge in case of conflicts.