From the sound of Skyforge’s first dev diary on pantheons (guilds), it sounds as though joining a group of players will be a near-mandatory move, especially if you want to reap the benefits of cool features like stat bonuses or special missions.
Pantheons will be easy to create but will require effort and resources to grow in its capabilities. One interesting feature is that guild leaders can create several clans to function as sub-guilds that officers oversee in order to share the load of leadership.
Individuals can benefit from being part of a pantheon by receiving character stat bonuses, special missions, and useful items. Pantheons can build up their own bases (strongholds) and participate in wars with other pantheons.[Source: Welcome to the Pantheon!]