I was inspired to write this class concept after reading about the "Fighting Friar" at Old Guard Gaming Accoutrements (a blog with an even longer title than my own). Mr. Palmer tackles the ill-fitting Monk class, clearing away the Oriental wushu and mystical powers to set a "Medieval Europe" tone for the class. In my version, the fisticuffs are almost forgotten, replaced by abilities I think a fantasy-world hermit could possess. To start, I'll note the big difference between the Cleric and the Monk/Ascetic. The Cleric is part of a coenobitic institution, a communal brotherhood typically recognized by the ruling government. Conversely, the Ascetic lives like a hermit or anchorite, socializing only when seeking wisdom from an elder, or when common folk seek his aid. Any "adventure" the Ascetic finds himself on is often due to the fact that Evil beings want him removed from their territory. Purposefully, the Ascetic resides in wilderness areas, dangerous caves, and haunted cemeteries to "challenge" his devotion and willpower. His hermitage, or skete, is usually little more than a single room or alcove, with his scholarly possessions and a prayer mat. As a rule, everything the Ascetic has must be a gift of charity or foraged/grown in Nature. To encourage donation, the Ascetic can barter his excellent calligraphy, which is widely known as a beneficial charm (see Holy Script in spell list). Since the Ascetic must complete exercises to stay healthy, he doesn't wear heavier armor than Studded Leather (and only if that was a charitable gift from an armorer). The weapon of choice for the class is a crosier, or pastoral crook, usually fashioned from a rare wood and passed down from a deceased elder. Like a cleric, the Ascetic can use any blunt weapon.

If a Cleric channels holy power from his deity, the Ascetic is more like a battery - storing/transfering holy power as it generates from his meditations and chants. Some of his spells are actually like scrolls and yoga forms. In gamer terms, the Ascetic is more about "protection" than dealing damage. The prime requisite is still Wisdom, but a player must also have at least normal Intelligence and Constitution. Here is my first pass at a spell list:

Level One: [standards] - Endure Cold/Heat, Remove Fear, Detect Evil, Detect Magic, Invisibility to Undead, Detect Disease, Animal Friendship

[new spells] - Holy Script (Can write a benedictive that has a 1% chance per level to aid the recipient. Calligraphy from hermits is legendary for a variety of feats, like the salvation of children from raiding monsters, the restoration of crops, etc). Weave Habit (Creates a complex knotted cloak that grants a holy armor bonus against evil equal to the Ascetic's Wisdom bonus. The Habit will only last for one day if worn in combat). Challenge Charm (While under the power of this mantra, all charms cast upon the Ascetic must pass a resistance check before the normal Saving Throw).

Level Two: [standards] - Chant, Augury, Detect Invisibility, Know Alignment, Silence 15' Radius

[new spells] - Fasting Day (Lessens the need for food to one bowl per day). Lend Life (Can heal others in 1d6/level measures, but no more than his own total HP). Challenge Thief (While under the power of this mantra, all rogue skill plied against the Ascetic are penalized). Script of Formlessness (Written scroll that allows the reader to assume a gaseous form for 1 round/level). Asana of Dexterity (Special exercise that grants the Ascetic and one disciple per 3 levels a Dexterity bonus for one day*).

Level Three: [standards] - Dispel Illusion, Protection from Fire, Protection from Paralysis, Remove Curse, Speak with Dead 

[new spells] - Script of Warding (Same as Glyph of Warding). Script of Castigation (Powerful rebuke that deafens/damages enemies when read, see Shukenja spell by the same name). Challenge Beast (While under the power of this mantra, non-intelligent beasts must pass a penalized morale check to attack the Ascetic). Asana of Vigor (Special exercise that removes fatigue and adds a +1 to most rolls). Asana of Purity (Special exercise that cures disease).

Level Four: [standards] - Detect Lie, Tongues, Protection from Normal Missiles

[new spells] - Empower Crosier (Imbues staff with energy, changing it to a magic weapon that does double damage to certain foes). Script of Exorcism (Same as Cleric spell). Script of Fates (A prophetic knowledge of the reader's future is learned). Invisibility to Evil (A Sanctuary-like spell that prevents detection by lesser evil creatures). Challenge Spell (While under the power of this mantra, all first and second level offensive magic cast upon the Ascetic must pass a resistance check before the Saving Throw). Asana of Strength (Special Exercise that grants a Strength bonus for one day). Asana of Antivenom (Special exercise that negates poison effects).

Level Five: [standards] - Detect Monster Type, Dispel Evil, Commune, Protection from Evil 10' Radius

[new spells] -Lend Existence (Can write a rune of resurrection, bringing the dead back to life but only so long as the Ascetic lives). Script of True Sight (Same as Cleric spell). Script of Hallowing (grants holy protections to a location, similar to Cleric spell). Challenge Spirit (While under the power of this mantra, the Ascetic gains extra resistance to undead/extra-planar attacks like level drain). Asana of Praxis (Special exercise that transfers a spell ability to another disciple for one day). Asana of Heavenly Wind (Special exercise that grants the ability to move as if Hasted and float as if Levitated). 

* - The Asana exercises can all be taught to one other individual per 3 levels, but if the student is not an Ascetic, he must pass a Wisdom check to gain the benefit.