Heart of the Mountain

The Heart of the Mountain (HotM) is a skill tree featured in the Dwarven Mines update that unlocks more levels by getting EXP for it, in turn unlocking more abilities and perks. 12 is required to use it. Blocks of coal are abilities while the normal coal are perks. Players can use only one ability at a time (they do not stack). In order to unlock more skills, players need to use Tokens of The Mountain, which can be obtained by increasing the tier of the Heart of the Mountain.

All of the HoTM upgrades work ONLY on public islands. They don't work on private islands.

Tiers
To level up the Heart of the Mountain, players can complete commissions from the King of the Dwarven Mines and take part in events which occur every 20 minutes. The first four commissions players complete every day will give significantly more HotM experience (900 HotM experience bonus additional to the base 100 HotM experience).

More info needed.

Skills
Needed Mithril Powder for Level x in Mining Speed is (x+1)^3