The Outpost is a building unique to the Polaris tribe that costs five stars, provides one population, and forms city connections with other Outposts that have three or fewer ice tiles between them. The building can only be built on ice.
When Polaris was released, the Outpost produced two population. This made Polaris overpowered since the Outpost not only granted Polaris a cheap and plentiful source of population but also allowed the tribe to upgrade its capital on turn 0, a very potent advantage. In response, the Outpost was nerfed in the next update to produce only one population.