Here is the full list of all 12 Ether Loop achievements.
Defeat the golem
Defeat the giant centipede
Defeat the wyvern
Defeat the molten spider
Defeat the corruption
Accumulate 10 items
Accumulate 15 items
Accumulate 20 items
Accumulate 25 items
Survive wave 1
Survive wave 2
Survive wave 3