I think I've found a bug, I've tryed to use expansion potion lv51+ wich says "drain cost -100%" in combination with other potions but mana is still drained from the pool by an augmented spell (with augment glyphs+ blast wand+ attune potion)
the plan was to first use mana potion (lv51) to have a massive mana pool, then freeze the pool using a spell that drains it so when the potion effect worns off I still have a massive pool for casting high cost spells.
I then use blast wand effect on "condense time" spell, then I use "atunement brew" (I think attunement brew multiply its effects with the blastwanded condense time) and I cast another condense time (after waiting for blast wand cooldown) wich is multiplyed further with the new conductor effect mutiplier on blast wand
the result is a spell increasing dramatically exp rate for artifacts (and brewing speed) at a high mana cost
thats where the idea of using high level expansion elixir comes from
problem: it doesn't work, I'll try using an elixir with less than -100% drain cost and update this message
edit: it seems to work fine with 99.9%