Ancient Valley

Spawns
Clay Man

Rock Golem

Black Imp

Bighorn Bison

Bosses
Colossus

Imp Overlord

Ifrit

Scavenger

Artifact
At the bottom left of the map there should be a small cave like structure ,if the "cave" ends with an Altar(Image 1) then this is the right map variant. Now you have confirmed that you are on the right variant climb up until you see a small 1x1 block missing out of the cliff (Image 2) ,go though the gap. Finally its a simple case of pressing all the buttons to activate the altar and gives you the Glass artifact.