Lane harass and sustained teamfight damage.
Empowered abilities and resource manipulation
Hitting an enemy champion with 3 attacks or separate abilities grants a burst of MS.
Shortly after using your Ultimate, gain a decaying Movement Speed increase that lasts for 3s and allows you to pass through units.
All movement Speed bonuses are 8% more effective on you.
Your first ability hit every 20s burns champions.
Creative tools and rule bending
Gain a free stopwatch. Stopwatch has a one time use Stasis active.
+5% Max CDR
+5% Summoner Spell CDR
+5% Item CDR
+6 AD or 10 AP
+5 Armor or 6 MR (match-up)
Phase Rush on Swain massively empowers your ability to stick to your opponent while casting your ult as well as being able to stay in range for follow-up [Q] damage.
Nimbus Cloak's massive burst of movement speed is great for chasing down enemies and getting to the back-line for a large explosion.
The bonus Movement Speed from Celerity is pivotal in re-positioning for landing a clutch [E] root and maneuvering with your [R] active in teamfights.
Scorch is an incredibly strong early laning rune for pressure and harassment. Look to proc the bonus damage as often as possible with either [Q] or [E].
Zhonya's and the stasis are a key part in taking over teamfights as Swain thanks to the ability to keep your [R] active and healing you throughout.
Cosmic Insight is an all-around fantastic rune choice for any champion as the extra bit of CDR helps you pump out more damage and stay safe with increased Summoner CDR.