This build is going to be short and to the point: the main priority of this build is to put you ahead and keep you ahead. If you are a skilled Pantheon and like to destroy games and not worry so much about your team or the enemy team and what they are building and so on then this is the build for you. To be honest it's not complicated at all and in a nut shell it's just a straight up off-tank ad brute build. Keep in mind that this build is set for people who are already skilled with Pantheon so I will not be covering some topics.

You might ask why I chose to go with armor pen marks and quintessences rather than AD runes. This is because normally when you are solo top you are versus a champion who if they're smart will have a decent amount of armor. Having the armor pen runes will be helpful by reducing that amount and you will still have a decent amount of ad at the beginning of the game since you will be getting 2 Doran's Blades. The seal and glyph runes are pretty basic however: a nice mix of armor and magic resist. The reason why the runes do not scale with level is because this build is centered around giving you a good early start.

The masteries here are also pretty basic. You might ask why choose the offensive tree rather than the defensive tree. A core reason to this is because with Pantheon's passive on his Heartseeker Strike ability it grants him a 100% crit chance to units below 15% health. Having the talents Executioner and Lethality helps to buff this passive. On top of that having the bonus armor pen and life steal that this tree gives you is very handy.

The Item build here is pretty straight forward, being fully built you end up with Mercury's Treads, Frozen Mallet, Bloodthirster, Warmong's Armor, Atma's Impaler, and then Youmuu's Ghostblade. There is a lack of magic resist but you will have an insane amount of attack damage and health to counter that. Keep in mind that this is an off-tank ad brute build. However, if you have a great start in the game, rather than getting Phage you can opt to get Bloodthirster first and Phage afterwards and then returning to the normal build.

Obvious picking summoner spells has to do with what champion and build you choose but I think that it's more about how you like to play. I prefer Flash and Exhaust because they provide a mix of versatility, offense, and defense. I believe that Flash is a must have for obvious reasons but on top of that it's really fun to be able to Flash Aegis of Zeonia combo.

So all in all this is a basic straight up bruiser build. If you get a good start you will definitely keep it with this build. If you do get a very good head start make sure to get your Bloodthirster before you get your Phage. Good luck hope you do well, pwn them noobs, and better your self as a pantheon!