I've found the rune that breaks Swain into viability

Ever since the mini rework, I've been testing out numerous builds. I've done all builds possible Tear start to Rylais, BFT to Cosmic, Liandry rush, and more. I've paided those builds up with Conq, Comet, Phase Rush, Grasp, Electro, and even Spellbook.

What surprised me the most what there's a single build that made Swain extremely playable and viable:

Rylai -> BFT -> Cosmic Drive/Liandry -> Cosmic Drive/Liandry -> Hourglass -> Tank

Conquer -> POM -> Haste -> Last Stand Magical Footwear -> Approach Velocity CDR + AP + flat HP

The main reason on how this build works is your 1st item powerspike, Rylais. Once you get Rylais, your movespeed is stupid high with Approach Velocity giving you a whopping 15% movespeed if you impair your enemy. With your R being a giant AOE with perma impair, even without boots you are ALWAYS able to chase down enemies.

Please try it and tell me if you have success with my build!