Here was my process:

1. I played as battlemage and saved as many potions of healing, haste and scrolls of teleportation as I could.
2. I got a ring of wealth and upgraded him to +7, so I had lots of potions and scrolls. This ring isn't vital though.
3. I used the crown to get the warping beacon ability and used a potion of divine inspiration to get the cost down to a minimum and the warp distance up to maximum.
4. At the Demon Halls cauldron, I brewed some shielding potions and upgraded a chalice to +10. I had also picked up a +3 ring of haste from the Imp. I transmuted the ring of wealth into a ring of energy +7 to power up the chalice. I was healing multiple hp per turn at this point. Ring of energy also recharged my warp ability super fast.
5. I brewed all my transmute scrolls into recycle spells and turned every potion I had into haste, invis, levitation or paralysis. I turned all my teleportation scrolls into phase shifts and brewed some displacement darts.
6. After yog, I was able to ascend very quickly due to all the potions of haste and invis that I had saved up. I was also able to use the warp beacon to teleport between once or twice each level of the ascent. It was enough though because I could heal and recharge at the boss floors. At the end I was taking 9 damage every step and had to use about 10 or so healing potions to get me through to the end.

Edit to clarify: I didn't kill anything while ascending, obviously killed stuff while descending :)