Unique takedowns grant permanent cooldown on your Ultimate.
Offense
+5 AD or 9 AP
Flex
+5 AD or 9 AP
Defense
+6 Armor or 8 MR (match-up)
WhyArcane Comet
Arcane Comet is a relatively abusable keystone for Lissandra thanks to the very short cooldown and slow on [Q]. [Q] harass with Comet and Scorch will result in a lot of chip damage during lane.
WhyManaflow Band
Manaflow Band is great for empowering your lane phase harass with [Q]. A successful [Q] proc means more mana sustain and more opportunities to wear down you lane opponent.
WhyTranscendence
Transcendence's mid-game utility allows you to spec into a more raw-AP-heavy build for burst damage to take over teamfights.
WhyScorch
Scorch is a fantastic lane harass rune, and pairs incredibly well with Aery to keep the pressure up.
WhyTaste of Blood
Lissandra's ability to repeatedly deal harassment damage makes Taste of Blood an incredibly reliable lane sustain tool for frequent damage trades.
WhyUltimate Hunter
As Lissandra your [R] is an incredibly versatile tool both offensively and defensively. More ults means more kill and survival potential.