The Deep Melting Drill is a powerful building in that can help you access resources buried deep within the Earth. With the Deep Melting Drill, you can better access Deep Deposits.
These valuable resources can keep your city alive for a long time, so long as they are harvested and properly used. Depending on the area, deep Deposits can provide resources like extra food or material.
These resources are nigh impossible to collect without the Deep Melting Drill, making it an important addition to your city.
However, you'll need to properly fund and Research this building if you hope to place it in one of your districts. You won't be able to build the Deep Melting Drill at the start of, but if you're playing Story Mode, you shouldn't have to wait long at all.
Near the end of Chapter 1, you'll be faced with a choice: either defeat the Frost or embrace it. If you want the Deep Melting Drill, you'll need to defeat the Frost.