Restore health over time based on your missing health.
Offense
+9% Attack Speed
Flex
+5 AD or 9 AP
Defense
+6 Armor or 8 MR (match-up)
WhyConqueror
Conqueror on Darius is incredibly strong in early 1v1 scenarios where you're able to build up a lot of passive stacks on the enemy, turning your bleed into a partial True Damage bleed.
WhyTriumph
Triumph's health burst nature synergizes incredibly well with Darius' reset on [R], keeping you alive to build stacks and dunk on another champion.
WhyLegend: Tenacity
Darius' biggest weakness is his lack of mobility, making him incredibly easy to be kited. The extra bit of Tenacity allows you to chase down and stick to your enemy for the kill.
WhyCoup De Grace
Coup De Grace's execution damage amp nature pairs perfectly with Darius' execution damage play style.
WhyRevitalize
Revitalize massively empowers your [Q] healing for those clutch teamfight moments.
WhySecond Wind
Second Wind's mid-fight heal/sustain is perfect for buying you time to build passive stacks and ramp as much damage as you can.