Swain Runes explained
There's one set of runes for Swain on patch 13.24 that is the clear favorite for LoL players and pros alike. The best Swain rune paths on the position 
Adc are 
Precision as the primary path and 
Resolve as the secondary path with a pick rate of 71%. Besides picking runes on Swain you should learn how to play Swain and if you are interested in pro matches take a look on how a pro builds Swain. If you want to discuss 
Swain then you should visit the champion subreddit.
Swain runes from primary path
Precision improves attack and sustained damage on Swain troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that 
Conqueror is the best keystone rune to run on Swain. This keystone rune provides additional power in the later stages of a game. As soon as Conqueror is fully charged, Swain deals additional damage and gains life steal. Other primary runes on Swain are 
Presence of Mind, 
Legend: Tenacity and 
Last Stand.
Presence of Mind helps Swain with the mana problems by restoring missing mana, if a champion is killed. Swain gains extra Tenacity with every additional stage of Legend: Tenacity. With Last Stand you deal more damage while you are at low health.
Swain runes from secondary path
When it comes to your secondary path, most Swain players prefer to go with Resolve. Resolve empowers the survivability of Swain and increases the tankiness. On the Resolve path, the best runes for Swain are Overgrowth and Conditioning.
Overgrowth increases your maximum amount of health. Conditioning powers up Swain tankiness after the laning phase.
FAQ for Swain Runes
Which is the best keystone rune on Swain?
The best keystone rune on Swain is Conqueror. This Swain runes setup is then referred as Swain Conqueror.
What runes does Swain use?
Runes from the paths Precision and Resolve are the most used runes on Swain. For the exact pick rates of Swain runes used, you have to study the rune distribution presented.