Ascending
Ascending is the process of exchanging experience for more character power: health, mana, and stats. After completing a necessary quest, you can ascend for health and mana by placing a succubus hair into the Mileth altar and speaking with either Deoch (health) or Gramail (mana). Furthermore, you can purchase stats in exchange for health or experience by speaking with Bedor in the Temple of Choosing in Mileth.
Ascension Quest
In order to be able to ascend, you need to complete the quest to slay the Bone Dragon at the bottom of the Kasmanium Mines, given to you by Ludar in Camp A'Chaid. After slaying the Bone Dragon, be sure to speak with Ludar again to fully complete the quest.
Pre-Max Stats
Experience
Please see the stats calculator to calculate how much experience is required to max your stats.
When ascending for stats directly at the Temple of Choosing, the experience cost formula appears to be as follows. Credit goes to Pablito for discovering this formula.
Let STAT be the current base value of the stat you're going to raise.
Before Transcending
XP COST = STAT * (BASE HP) * 17
After Transcending
XP COST = STAT * (BASE HP) * 20
Example
For example, if my base HP is 5000, haven't transcended, and I want to raise my strength from 100 to 101 then it will cost:
XP COST = 100 * (5000 * 17)
XP COST = 8,500,000
Post-Max Stats
When increasing stats beyond the your class-specific maximum for that stat, the cost to increase the stat is as follows:
Let STAT be the current base value of the stat you're going to raise.
XP COST = STAT * 500,000
Example
For example, if I am a Warrior, and I want to raise my strength from 250 to 251:
XP COST = 250 * 500,000
XP COST = 125,000,000
HP
Please see the HP calculator to calculate how much experience is required to increase your HP.
When ascending for health by speaking to Deoch, the experience cost formula appears to be as follows:
50 HP
XP COST = (BASE HP) * 500
500 HP
XP COST = (BASE HP) * 5000
It is most efficient to buy 500 HP at a time, as you pay the cost relative to the starting point, rather than the increased cost at every 50 HP increment.
MP
Please see the MP calculator to calculate how much experience is required to increase your MP.
When ascending for mana by speaking to Gramail, the experience cost formula appears to be as follows:
25 MP
XP COST = (BASE MP) * 500
250 HP
XP COST = (BASE MP) * 5000
It is most efficient to buy 250 MP at a time, as you pay the cost relative to the starting point, rather than the increased cost at every 25 MP increment.
Remarks
You should consider only purchasing stats with experience when your HP is at or near its minimum (4000). When done this way, you will spend less experience overall when maxing your stats.
Once a particular stat is higher than 150, it may be more effecient in terms of experience to purchase stats one by one by ascending for 250 HP and turning that HP into one stat. However, this will require you to use a Succubus hair for every stat point placed using this method.