Altar

Making an altar
To build an altar, you first need to build a forbidden knowledge center and research Altar. Researching Altar of Sacrifice and Human sacrifice will unlock tier 2 and tier 3 altar respectively. An altar can be upgraded for free by clicking on it and selecting Upgrade altar.

Worship
The easiest way to gain deity's favor is to hold a sermon. Sermons can be held on an altar by a preacher. Room with an altar is designated as a temple. By clicking on the cult altar, you can set the deity workshipped, the preacher and also set daily morning or evening sermons. Morning sermons happen between 6 and 10 in the morning while evening sermons happen between 6 and 10 in the evening.

When a sermon starts, the whole colony will gather to listen to the preacher. If the preacher is drafted or incapacitated, the sermon will be cancelled. The amount of favor gained from the sermon depends on the preachers social skill and gains a bonus if the preacher wears cultist clothing.

Sermons can give cultists positive or negative thoughts, always positive thought to the preacher and always negative thought to the people not belonging to cult.

Good social skill on a preacher gains more favor to the deity, more cult mindedness to all colonists and a higher chance of good thoughts for the cultists.

Sacrifice
When researched, cultists can sacrifice food, animals or even humans to gain deity's favor. The amount of favor gained depends on the executioners social skill and the amount/value of things sacrificed.

Human Sacrifices can have a variety of side effects, sacrifices can either be a complete success, mixed success which also creates a side effect, pretty failure, or a failure with a side effect.

The success of a sacrifice depends on a 100 sided dice roll against a base spell difficulty. Tier 1 spells require a roll of at least 40, tier 2 spells 50 and tier 3 spells 60. You can influence the roll by making use of favorable factors and can review the roll on the altar if you have the Chronicling research. Favorable factors and their bonuses to the roll include:
 * Eclipse took place (+5)
 * Aurora took place (+5)
 * Executioner is experienced (no previous sacrifices is -10, three or less is -5, more than ten is +10)
 * Attendants wore cultist clothing (max +15 if everyone wore cultist clothing)
 * The executioner wielded a sacrificial dagger (+5)
 * A statue of the appropriate deity was nearby (+10)
 * The statue was a good quality (max +10)
 * Temple is impressive (max +5)
 * Temple is wealthy (max +5)
 * Temple is spacious (max +5)
 * Temple is beautiful (max +5)
 * Temple is clean (max +5)
 * All special astral events (excluding Star are Right) lower the chance of a succesful sacrifice down to -50

Successful sacrifice will give positive thoughts to cultists but negative thoughts to anyone who is not a part of the cult.