The Portal Goblins are a violent group of goblins and hobgoblins who attack and eat the exiles who come through the Portal. They appear to be based out of the Goblin Castle, although the immediacy of their attacks suggests the possibility that they may have also set up camp in the vicinity of the Portal.
According to Bruno, the Portal Goblins are friendly with the local non-goblinoids, and only attack those who come through the Portal because they are 'different'.
Based on the initial encounter with them, it appears the Portal Goblins are poorly equipped overall. They attacked primarily with clubs, although some had morningstars and javelins. They all wore low-quality hide shirts for armor. They maintained some traps in the area around the Portal to catch those who came through. They attacked with goblin dogs, which they may have also used to track those who come through the Portal.
In all, there were only 22 of them at the main portal, and the Portal Goblins did not attempt to attack us at night while we stayed at the castle. This implies that either they do not have a means of tracking us, or they either had inadequate resources to overpower us, or they had more promising opportunities during the night of day one.
The drow prisoners told us that they periodically raided goblin caravans traveling through the badlands.