I'm so confused about the last character and how to get them, from another comment I read that the name of it was nav, and I know you build them from said comment, but what do you use to build them?

Travel around in the icy biome and you will find a blueprint. There are 2 different tiles in the icy biome, the darker tile with one tree is the one you want. First tab costs: 999 ice 999 lava rock 999 water