Blast the sandstone, stop the cave creatures, climb out the shaft.
Beetle · 100
Hunter · level 3+ · 200
Borer worm · level 10+ · 300
Armored beetle · level 12+ · 400
Fuse rat · level 18+ · 300
Cave bat · level 20+ · 400
Splitter slug · level 22+ · 150 + 2×50
Stone golem · level 25+ · 800
Gas beetle · level 28+ · 500