Pantheon Runes explained
There's one set of runes for Pantheon on patch
11.19
that is the clear favorite for LoL players and pros alike. The best Pantheon Runes on the position 
Support are Precision as the primary path and
Inspiration as the secondary path with a pick rate of 80%. Besides runes you should take a look on Pantheon Build and if you are interested in pro matches take a look at Pantheon Probuilds. If you want to discuss
Pantheon then you should visit the champion subreddit.
Primary path on Pantheon
Precision improves attack and sustained damage on Pantheon 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
Pantheon. This keystone rune provides additional power in the later stages of a game. As soon as
Conqueror is fully charged, Pantheon deals additional damage and gains life steal. This is usually followed up by taking
Triumph,
Legend: Tenacity and
Coup de Grace.
Triumph restores on Pantheon a part of missing health and award bonus gold, if a champion is killed. Pantheon gains extra Tenacity with every additional stage of
Legend: Tenacity. Pantheon deals with
Coup de Grace more damage to targets with low health.
Secondary path on Pantheon
When it comes to your secondary path, most
Pantheon players prefer to go with
Inspiration.
Inspiration opens creative opportunities on Pantheon troughout the match. On the
Inspiration path, the best runes for Pantheon are
Hextech Flashtraption and
Biscuit Delivery.
Having an extra way to decrease the distance with the
Hextech Flashtraption will make an engage much easier to pull off.
Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes.