Sapphire-polished Drill Engine

The Sapphire-polished Drill Engine is a Drill Engine that can be obtained from forging in The Forge in the Dwarven Mines. It increases Drills' by  and  by  (secret bonus).

Obtaining
The Sapphire-polished Drill Engine can be forged once the player has reached Heart of the Mountain Tier 5. It takes 20 hours to forge.