Ascetic is a role modifier (though it can function as a role in its own right) that causes a player to be immune to all actions at Night except kills. More precisely, Ascetic reflexively Roleblocks all actions taken against them except kills.
When combined with other power roles, the Ascetic modifier creates roles that cannot be tampered with directly, but are immune to beneficial actions as well. For example, an Ascetic Cop cannot be Roleblocked, but also cannot be protected by a Doctor.
This role modifier is considered Normal on mafiascum.net. An Ascetic role cannot be targeted by anything other than a kill. A role attempting to target an Ascetic should be seen doing so by Trackers and Motion Detectors. Investigative roles (Cops, Role Cops, Watchers, etc) should receive "no result" if attempting to investigate an Ascetic role.
Use and Power
By being unable to be tampered with, Ascetic roles lower the swing of games in which they are employed. Ascetics are a nuisance when Town because they cannot be protected or investigated, so Ascetic is more often used as a modifier to power roles so as to temper their power somewhat. Non-Town Ascetics get much more out of the Ascetic modifier, as they generally have no need for protection from kills but very much value immunity to investigations, roleblocks, redirects, and so forth.