Archmages are mages of exceptional power that have reached an understanding of their chosen Sphere beyond the scopes of normal Masters (by attaining the sixth dot). Their Nephandic counterpart are the Aswadim, who are masters of the Qlippothic Spheres instead and strive for all-encompassing Descension.
To be an Archmage is to break the limitations one had imposed on one's own power. Akin to an Awakening Sleeper, the Archmage realizes that he is capable of things he thought impossible by diving deeper into his chosen Sphere. Their study, however, is far from over, as different levels of power await for Exemplars and Postulants, who later have the chance to either Ascend or stay as Oracles to guide others.
It is nearly impossible to reach Archmastery without the support of existing Archmages, and not every mage has what it takes to become an Archmage. Those who passed the Threshold usually claim that they were driven by their Avatar since their Awakening through harrowing Seekings and similar obstacles to reach Ascension. Most Archmages show a combination of ambition, a thirst for knowledge, personal responsibility and sheer power. Other Archmages watch their would-be peers for every sign of failure or corruption and handle dangerous adherents by themselves.
Most Archmages are also dependent on support from their paradigm. It can be difficult to reach Archmastery when one fails to understand the basics of one's own belief system. Each Tradition, Craft and Convention favours different characteristics in their Archmages and Masters that are carefully cultivated.
Most Archmages discharge their Resonance even without casting a Spell, making them easily detectable. As such, these beings are plagued by potent Paradox that makes a mundane life nearly impossible. However, they are encouraged by their peers to maintain connections to normalcy, in order to avoid the greater streaks of Hybris - the events surrounding the fall of Horizon and Doissetep show how dangerous it can be for mages to seclude themselves from reality into self-created umbral realms, and Archmages are no exception to this.
Because they become increasingly disconnected from the Consensus the more power they amass, most Archmages are eventually barred from contact with the mundane world, forced to dwell in Horizon Realms. Some stay in contact with humanity by keeping small Sleeper communities in their Horizon Realms, while others keep contact with different, long-living supernaturals, like Cainites, Wraiths or Mummies - and there are those that simply go mad. Be that as it may, Archmages are usually valued guests in Umbral Courts.