Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
While I usually just look over the builds, after looking at the Heimer builds, and not really seeing the start I had done, I figured I may as well try to put up my version of Heimer build. While this may not be the highest AP you can get out of him, I find having the seals and chalice makes it much easier to keep his battery running. Hope you guys like this.
Also to note, I have no reached 30 yet, so the build is somewhat guesstimated, but I will try to update it as I reach 30 and I am always open to suggestions.
Runes are preety straight forward, Greater Mark of Magic Penetration for Magic Penetration, Greater Seal of Scaling Mana Regeneration for sizable mana regen, especially late game, and Greater Glyph of Scaling Ability Power for extra AP mid and late game.
Quints are up in the air really, as currently I'm building my page. Potency, Focus, Insight, and Fortitude however are not bad choices. AP Seals at the cost of mana regen aren't too dangerous as well.
I use a 9/0/21 build for Mana Regen, Archaic Knowledge, Greed, Extra XP, and reduced cooldowns for Ghost and Clarity. I start Utility with Good Hands cause Preserverance doesn't give a sizable different in regeneration above first level. Ghost and Clarity masteries are of course also active.
For skill sequence, I build turret, rocket, grenade, and build both turret and rocket to three, and then max out rocket, turret, grenade(getting upgrade when available). This sequence gives good power to your multi-tool Kiting ability, and gets you the twin turrets early.
If your good with the skill shot although, maxing the grenade before the rocket also works.
I start the game with Meki's Pendant which I quickly upgrade it to Feindish Codex once the opportunity presents itself. The codex to me is an excellent start for Heim with the AP/Mana Regen/CDR to start him off. I then buy Boots of Speed which I upgrade to Sorcerer's Shoes although if you want more CDR for faster rockets Ionian Boots of Lucidity are not a bad idea.
At this point I build Chalice of Harmony together with the codex, these two items will net you nearly 28mana/5 when Heimer is low on mana, and this doesn't include self regen or runes. The two items and clarity should keep you well stocked on Mana through the end of the game.
After the Chalice is purchased, I build Rabadon's Deathcap for the AP, and finish Morello's Evil Tome. After the Tome, the items are situational, although Rylai's Crystal Scepter, Lich Blade, Will of the Ancients and Abyssal Scepter are some good choices.