Rend stacking, lane dominance, and item efficiency
Improved attacks and sustained damage
1.5s after damaging a champion gain a large amount of attack speed. Lethal Tempo allows you to temporarily exceed the attack speed limit.
Excess healing on you becomes a shield.
Takedowns on enemies grant permanent Attack Speed.
Deal 7% more damage to low health champions. Gain AD/AP after kills or assists.
+18% Attack Speed
You get free boots at 10 min. but you cannot buy boots before then. These boots give additional MS. For each takedown you acquire the boots 30s sooner.
+5% Max CDR
+5% Summoner Spell CDR
+5% Item CDR
Kalista is all about building as many [E] stacks as she possibly can to execute her targets and the burst of Attack Speed from Lethal tempo lets you do just that in a manner of seconds.
Overheal is a rune that synergizes well with Kalista's natural Life Steal item build to keep her topped off with a shield.
Kalista is all about attacking fast to build [E] Rend stacks. Alactrity's bonus attack speed directly translates to a faster Press the Attack proc and more damage.
Coup De Grace works fantastically with Kalista's desire to execute her targets with [E].
If you find yourself playing into a number of tanks, Cut Down is also a strong option.
The free gold value of Magical Footwear lets you spend that gold on earlier item power-spikes for more damage.
Cosmic Insight's all-around effectiveness makes it great for lane safety with the bit of Summoner CDR as well as the opportunity for more damage with the ability CDR.