Your first attack against an enemy champion slows them (per unit cooldown). Slowing champions with active items shoots a freeze ray at them, creating a lingering slow zone.
Unique takedowns grant permanent Active Item CDR (includes Trinkets).
Offense
+5 AD or 9 AP
Flex
+5 AD or 9 AP
Defense
+6 Armor or 8 MR (match-up)
WhyGlacial Augment
Glacial Augment on Veigar open you up to a build where you can build Twin Shadow and GLP to set yourself and team up for a controlled teamfight.
WhyPerfect Timing
Perfect Timing doubles down on your ability to stay safe in lane and scale into the mid to late game. After using your Stopwatch, don't be afraid to sell the broken watch for a bit of extra gold to hit an earlier Deathcap.
WhyMinion Dematerializer
Minion Dematerializer is great for patching up Veigar's weak early game wave clear so that you can match roams with the enemy mid for jungle skirmishes.
WhyCosmic Insight
Cosmic Insight further empowers your ability to stay safe in lane with short Summoner Cooldowns and the extra bit of CDR helps you to build your stacks even quicker.
WhyTaste of Blood
Taste of Blood empowers your ability to healthily sustain the laning phase so you can build your passive stacks and scale into your mid-game 2 item power-spike.
WhyIngenious Hunter
Ingenious Hunter is especially good on this Glacial Augment build as it will drastically reduce the cooldown of your 2 primary items; Twin Shadows and Hextech GLP