With this entry I begin to details encounters involving the new kids on the block - Aeons. These are probably my favorite addition to the Pathfinder mythology. Finally some cool and mysterious champions of Neutrality!
The Blue God (CR 12 or 13 with heretics and humanoids)
This encounter can be used when the adventurers are passing through wildlands close to mountains inhabited by savage humanoids. While crossing the region the party hears a rumor about "The Temple of the Blue God". This heretic sect dominated a fortified temple responsible for keeping the humanoid barbarians at bay. Its leaders are old bandits and exiles of region's towns, converted to the mysterious Blue God, a demon that cursed the paladin champion of the temple to a death-like sleep. The heretics received help from two humanoid tribes of the mountains, impressed by the power of the Blue God. This demon resides within the inner sactum of the fallen citadel. The body of holy champion is guarded by the last clerics of the order in one of the towns. The priests are forced to constantly change their base in order to stop the heretics from claiming the paladin's body.
Actually, there is no "Blue God". The current crises started when an akhana (an aeon devoted to life and death) manifested in the region. The creature assaulted the temple and stole the paladin's soul. After that, the aeon lured local bandits to recruit some humanoids to defend the temple. It didn't present itself as a deity, but the humans and gullible humanoids saw it as one. Guided by the unfathomable commands of the Monad, the akhana took the paladin's soul to stop him from destroying the humanoids tribes. The fortified temple was the heart of a small crusade guided by the holy champion against the local savages. The akhana's actions are in fact an attempt to keep the balance of life and death in the region. If the humanoids are slain, their tribes will stop the sacrifices that keep an ancient evil in slumber below the mountains (a demon or ancient dragon). If this evil arises, all the life in the region will be extinguished.
The neutral outsider is searching for a portal to leave the Material Plane with the paladin's soul. It doesn't understand concepts like good or evil, only life and death, seeing the paladin's actions as detrimental to the local balance of forces. If the party attempts to dialogue with the aeon, they may be able to glimpse scenes of destruction and death arising from the mountains. Further investigation may lead to the unhallowed cavern where the tribes maintain their bloody rituals.