Welcome everyone to my personal Skarner build! This build will give Skarner a very durable play style while still maintaining a threatening presence due to his additional ability power.

I choose marks of Magic Penetration as my skarner build deals mostly magical damage.
I choose seals of Flat Armor to give him strong resistance to early game harassment.
I choose glyphs of Magic Resist per level to shore up the natural weakness to magic damage.
I choose Quintessences of Magic Resist per level for the same reason as my glyphs.

Standard mastery tree for a tank with points into offense for more magic penetration.

I start with a Regrowth Pendant because this build is designed for a Skarner taking solo top in order to ensure lane sustainability. Building into a Philosopher's stone to help with gold income and the early game mana trouble Skarner typically has.

The Chalice of Harmony is built next for the early magic resistance and to ensure Skarner's lane dominance by securing his mana problems early game.

The Ninja Tabi are built next to synergize with the masteries to give a 14% dodge chance and to cause dodges to speed Skarner up, assisting with chasing and escaping enemies.

The Sunfire Cape and Abyssal Scepter combo build up his armor and magic resist respectively while giving his crystal slash a nasty combo of holding the enemy in the sunfire damage and making them more susceptible to magical damage.

The Rylai's Crystal Scepter is used to increase Skarner's max health as well as increasing his magical damage and healing via Fracture, and to cause his crystal slash to be even harder to escape from.

The Shurelyas's gives more mana regen to ensure Skarner will never have mana trouble, health to increase survivability, and the useful on use to secure kills and aid retreating teamates.

The reason I choose fracture over Crystal Slash is that it can be used to harass ranged opponent through minions waves and then the wave can be hit with crystal slash (or sunfire cape damage at mid game) to consume all the marks for large amounts of health. This build does not include as many HP regen items that tanks typically have. So Skarner needs Fracture to be able to maintain his presence in the lane against opponents.

Teleport is used to allow Skarner to buy items when needed or heal up and quickly return to the lane so as not to miss out on experience and money from minion kills.

Fortify is used to make last hitting minions early game much easier and to help turrets/allies across the map. Also the Impale ultimate and Fortify combination can almost always ensure a kill.

This is my first guide, please try it before voting or criticizing please. Feel free to leave comments and advice/observations about the build! Go out and show your enemies the might of the Crystal Vanguard!