A great mist descended on Western Connaught, and when it lifted the Firbolg discovered that a fortified camp had been built. They approached the fortifications, where they were met by a group of beautiful, tall, fair people. They curiously examined each other’s weapons. The weapons of the Tuatha were light, bright and sharp, and the weapons of the Fir bolg were blunt and heavy. They agreed that the two races should divide Ireland equally, and join to defend the territory against all newcomers.
Source: Tuatha Dé Danaan