Here is the full list of all 25 Creature in the Well achievements.
Activate the Power Reserves
Charge 7 orbs at once
Generate 1,000 power in one hit
Get thrown out of the machine
Open the temple
Try to escape the sandstorm
Find a secret strike tool
Find a secret charge tool
Upgrade your BOT-Core
Unlock the Support Monoliths
Unlock the Weather Control Monolith
Enter the Creature's well
Save Mirage from the sandstorm
Let's play
Find all the lore
Heal a total of 1,000 health absorbed from anomaly balls
Destroy 100 drones using EMPs
Help Roger mop the floor
Hit 20 bumpers with one shot
Fully upgrade the BOT-Core
Find all of Danielle's tools
Find all capes
Find the scavenger's hidden stash
Find Phillip's prototype
Generate a total of 2,000,000 power