I've come so close, and failed twice.
Once, I made it to the astral plane with a gaggle of dragon pets, several restore mana potions, and a real effective knack for charming the various priests and acolytes to take care of the three horsemen. I saunter up to the middle altar and sacrifice the amulet... but due to a complete lack of presense of mind, I got my dieties confused and sacrificed the amulet on the wrong altar. I believe the score page gave me credit for escaping but not ascending, with the caption "escaped from the dungeon in celestial disgrace".
The other time I made it to the astral plane, I got cornered by "Famine", and was starved to death not more than 50 paces away from the altar.