Xerath Runes explained
There's one set of runes for Xerath on patch 14.9 that is the clear favorite for LoL players and pros alike. The best Xerath rune paths on the position 
Mid are 
Sorcery as the primary path and 
Inspiration as the secondary path with a pick rate of 40%. Besides picking runes on Xerath you should learn how to play Xerath and if you are interested in pro matches take a look on how a pro builds Xerath. If you want to discuss 
Xerath then you should visit the champion subreddit.
Xerath runes from primary path
Sorcery empoweres abilities of Xerath and increases the available champion resources. Most of high elo players – and our LoL pros in the the major regions – have agreed that 
Electrocute is the best keystone rune to run on Xerath. This keystone rune provides burst damage, aiding them in nuking down the enemy carries. Other primary runes on Xerath are 
Manaflow Band, 
Transcendence and 
Scorch.
This is usually followed up by taking Manaflow Band for additional mana and mana regenaration. Transcendence for some more Ability Haste. Scorch increases your control in the early game.
Xerath runes from secondary path
When it comes to your secondary path, most Xerath players prefer to go with Inspiration. Inspiration opens creative opportunities on Xerath troughout the match. On the Inspiration path, the best runes for Xerath are 
Biscuit Delivery and 
Cosmic Insight.
Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes. Cosmic Insight grants summoner spell and item haste.
FAQ for Xerath Runes
Which is the best keystone rune on Xerath?
The best keystone rune on Xerath is Electrocute. This Xerath runes setup is then referred as Xerath Electrocute.
What runes does Xerath use?
Runes from the paths Sorcery and Inspiration are the most used runes on Xerath. For the exact pick rates of Xerath runes used, you have to study the rune distribution presented.