Sacrificing

Overview
Fuel can be sacrificed in Ancient Hearths to temporarily gain powerful positive effects. Sacrificing is extremely resource intensive and requires significant labor investment, or even restructuring of the whole settlement, should you wish you keep it up for an extended period.

Sacrificing mechanics


You can Sacrifice up to 3 stacks of, , , or. Each fuel's Sacrificing stacks are independent. To choose how many stacks you want to Sacrifice, use the green arrows next to the fuel type. Activating Sacrifice immediately consumes 1 unit of fuel, even if you are paused. If you only have 1 unit of this fuel to begin with, you will keep the effect for as long as you are paused. If you don't have any fuel of one type, its green arrow is going to appear grayed out. Do not forget to reset the stacks to 0 once the need for Sacrifice has passed - you will quickly run out of fuel otherwise. There's also a checkbox to Stop after storm.

There are 3 visual indicators of Sacrificing taking place:
 * An orange aura around the Ancient Hearth.
 * A Perk in a gray outline with the number of stacks in the Perk section on the bottom left of the screen.
 * An exclamation mark in a yellow diamond next to the fuel Resource Category in the upper section of the UI. It says "You are sacrificing fuel in the Hearth." if you hover over it.

Sacrifice effects
Each fuel type grants different boons:

Sacrificing efficiency
There are 2 modifiers that affect Sacrificing efficiency, outside of Cornerstones:
 * Sacrificial Flame: resources sacrificed in the Ancient Hearth burn 10% longer. A Monastery of the Vigilant Flame level 7 upgrade.
 * Prestige 18: the Ancient Hearth seems to have a defect. No matter how hard the firekeeper tries, sacrificed resources are burning 35% quicker.

The table below shows how much fuel you need to Sacrifice per stack to keep the effects, depending on your upgrades and Difficulty: