The information on this page pertains solely to newlandsKingdom: New Lands
The Signpost is a naturally generated structure found deep in the Forest biome. The Monarch may "buy" the map hanging from it, unlocking a new feature for future Kingdoms. There are various kinds of unlockable features in the game, including new NPCs, Special Tower Upgrades, Shrines, and Mounts. The upgrade that a signpost unlocks is random but constrained to the possibilites of the island it's on. Once all upgrades on an island have been purchased, the Signpost still can still appear in the forest but without a map attached, and it cannot be interacted with.
A total of 13 different structures and NPCs can be unlocked. To be unlocked, the Monarch has to pay 2 coins to a Signpost in the forest for its map. The unlocked feature will only be revealed on the end to the current Kingdom, either through escaping to new lands or the Crown falling to the Greed. Each island has one to four different unlocks, but only one can be found at a time.