Notch Rock is one of the game's resources.
They are obtained through:
- Battles and Level Taxes in any scenario in Hard Mode.
- The last of daily Online Rewards
- Daily Login Reward (random)
- Some events
- Mysterious Store (random)
They are used on tower research at the Engineering Quarter. At the start of the game, they will be as important as the Dark Soul Crystals will become later on and it may seem that you're always lacking these, but afterwards you'll have a huge surplus. Unfortunately they are only worth 20 gold each if you sell them. Just concentrate on unlocking Hard scenarios and center your Level Tax collections on them (they are also the most lucrative by far) and soon you'll have more than enough.
Other uses
- Second Training Ground slot and upgrade
- Second Supply Station upgrade
The max stack of Notch Rocks is 999.