Premise behind this build - This build takes advantage of the new Mysteria mechanic, whereby more expensive spells (such as CYDSTEPP) now build piety with the god far quicker than they did previously. It essentially works similarly to the Paladin/Mysteria build, except instead of having a massive mana pool for healing, you now have a massive mana pool for CYDSTEPP.
Similar to the paladin build, the mana potions become ridiculously good as they're based on your total mana pool, and by the end you'll be able to cast 1-2 CYDSTEPPs per mana potion, and 3-4 with full mana. In addition you also get the benefit of the innate warlord attack bonus after consuming a mana pot. Furthermore, because most of your fighting will be done on 1 health, you'll also be getting the most out of the Warlord's "determined" ability which adds 30% attack bonus when you fight with low health.
Essentially this build takes the Warlords assortment of bizarre abilities and maximises the effectiveness of each one.
Race: Gnome. This build benefits hugely from mana pots, so gnome is easily the best choice. Convert everything, don't worry about pissing off the god because it only increases monster magic resist which you don't care about.
God: Mysteria. Constantly use the 'magic' boon to get a higher mana pool, again the magic resist doesn't matter as you'll be using your sword.
Items: By far the best item to use with this build is the Avatar Symbol (100% attack bonus when fighting with less than 25% health) but if you don't want to spend 200 gold on this prep then anything with good damage or more mana is nice. Don't bother with health though because your max health won't really matter with this build.
Scout: Altar is pretty much essential. Everything else is optional.
At the start you want to grab Mysteria worship and then spam CYDSTEPP as much as possible, if you're full on mana and already have death protaction just pick a random high level mob and let it kill you so you can cast CYDSTEPP again to build piety. Take magic boon whenever you get more than 10 piety, as you'll be pissing off the god a lot from fighting and so you don't want to lose more piety than you need to. Leave an ENDISWAL or Fireball glyph on the ground for later when you want to build piety without losing health.
Basically if everything goes perfectly you'll have about 40 mana by the time you take on the boss, enough for 4 CYDSTEPPs and you'll have a nice stockpile of mana pots for even more lives. You'll also be able to take advantage of the refreshment boon should you need even more mana, since you'll be building up piety while fighting the boss.