Ramping damage, lifesteal/sustain, and scaling ramp damage.
Improved attacks and sustained damage
Attacking a champion 3 times will expose them, dealing bonus damage and causing them to take more damage from all sources for 6 seconds.
Excess healing on you becomes a shield.
Takedowns on enemies grant permanent Lifesteal.
Deal 7% more damage to low health champions. Gain AD/AP after kills or assists.
9% attack speed, 10 ability power or 6 attack damage
Gain 3% extra MS. Gain extra AP or AD, based on your bonus MS, Adaptive.
Gain increasing amounts of AD or AP, Adaptive over the course of the game.
Press the Attack's exposure damage synergizes incredibly well with BotRK + Black Cleaver + [R] shredding even the tankiest champions.
Overheal is a great rune for topping off your heal to sustain chip damage from the enemy, and synergizes well with the Life Steal from BotRK and Bloodline.
More Life Steal means longer trades equalling Lucian gets off more Passive procs and Press the Attack damage.
Coup De Grace is a great rune for finishing of the last bit of health on champions you have shredded with Black Cleaver and Press the Attack.
Lucian's low auto-attack range makes him vulnerable when looking to attack. Celerity's bonus Movement Speed helps you to kite around your max range for more safety and mobility.
Gathering Storm is your late game insurance policy. Paired with Press the Attack, your late game single target dueling damage will be massive.
Patch 8.10 saw a buff to Phase Rush and jungle duels for scuttle making Xin a powerhouse.