In Risk of Rain 2, Newt Altars are small blue rocks, with lighter blue spikes, that can spawn in various locations in the game’s stages. If you give one of them a Lunar Coin, they will open a portal to the Bazaar Between Realms when the boss fight for that stage is over.
You also need to find, and activate, seven unique Newt Altars to complete the Newtist challenge, and unlock a new item. This guide is not yet complete, as it is not easy to find these randomly spawning Newt Altars! But I will be keeping it updated over the coming days.
Newt Altar Locations
You can find a Newt Altar on a small outcropping of rock in the area with the door to the secret boss fight. You might need some extra items to get to it though!
Head for the shore of the lake, and follow it around along the narrow strip of land between it and the cliff face. Head for the trees, and you might find a Newt Altar there.
You can sometimes find a Newt Altar behind the large broken wall that right beside a large stone circle near the edge of the map.
Located on a ledge overlooking the rest of the map, you need to use one of the water geysers to get up here.
This one is located behind the big door at the bottom level of Distant Roost. You need to get lucky and have the door be open, but if you have a dash, you should be able to squeeze through the gap in the door.