Viktor Runes explained
There's one set of runes for Viktor on patch
11.8
that is the clear favorite for LoL players and pros alike. The best Viktor Runes on the position 
Mid are Sorcery as the primary path and
Inspiration as the secondary path with a pick rate of 84%. Besides runes you should take a look on Viktor Build and if you are interested in pro matches take a look at Viktor Probuilds. If you want to discuss
Viktor then you should visit the champion subreddit.
Primary path on Viktor
Sorcery empoweres abilities of Viktor and increases the available champion resources. Most of high elo players – and our LoL pros in the the major regions – have agreed that
Phase Rush is the best keystone rune to run on
Viktor.
Phase Rush offers more flexibility and options to betake oneself in and out of danger, which can be helpful since that's essentially the main playstyle of Viktor. This is usually followed up by taking
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.
Secondary path on Viktor
When it comes to your secondary path, most
Viktor players prefer to go with
Inspiration.
Inspiration opens creative opportunities on Viktor troughout the match. On the
Inspiration path, the best runes for Viktor 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.