Ritual modifiers

Rituals are harder or easier, and cost more or less gp, depending on the circumstances under which the ritual is performed. You are informed of these bonuses or penalties when performing a ritual.

Bonuses

All deities

You'll get a bonus if...

• You are at a high altar of your deity.
• You're near a high altar of your deity. You seem to visibly get the bonus if you're in the same city as a high altar, or within a few miles of one.
• You have been "actively worshipping" your deity. If you've recently prayed, used a ritual burial command, or put an appropriate item in your own deity's newbie chest, you'll get this bonus.

Unique

• Pishe: When outside in the rain, snow, or sleet.
• Gufnork: When you have enough (seven?  research If this has been marked on a page, it's because there was something that probably isn't known, that the person who edited the page thinks could be found out. Perhaps you could figure this thing out, and be famous evermore. ) fluffy items in your immediate inventory.
• Gapp: When you're wearing enough (three?  research If this has been marked on a page, it's because there was something that probably isn't known, that the person who edited the page thinks could be found out. Perhaps you could figure this thing out, and be famous evermore. ) stylish items. Also, when you're in stylish surroundings (your passage room).
• Sandelfon: When you're indoors.
• Fish: When you're in water.
• Hat: When you're at another deity's high altar, or are with at least four other priests.
• Sek: When you're in combat.

For specific rituals

• Mend is easier for Gappics when performed on a stylish item of clothing.

Penalties

All rituals

You'll get a penalty if...

• You "sense that the gods have averted their eyes from this place", that is, you're in a wizard's guild or witches' guild outpost, or you're in real estate owned by a witch or wizard. This penalty seems to be larger for Resurrect than for other rituals.
• You're at another deity's high altar and are not a Hattite.
• You're poisoned.
• You're drunk.
• You're performing the ritual from a faith rod (the extent of the penalty may depend on your faith.items.rod bonus).
• You are far from a high altar of your deity.
• You "can barely sense the presence of <deity>", meaning you're nearly out of alignment.

Specific rituals

• Mend is more difficult for Gappics if the clothing you're performing it on is "an abomination unto Gapp". Clothing that's the opposite of a colour that's stylish seems to be specifically unstylish--so if red clothing is stylish, green clothing is unstylish.
• Feedback is more difficult if your hands are full.
• Major Shield is much more difficult if you're using a shield that is not a proper shield--that is, a "shield" that can't be used to block.
• Resurrect is rumoured to be more or less difficult depending on the manner of death, although this does not show up as a visible ritual modifier.  research If this has been marked on a page, it's because there was something that probably isn't known, that the person who edited the page thinks could be found out. Perhaps you could figure this thing out, and be famous evermore. 
• Rituals that require the power of sight are more difficult if it's dark. (See: Rituals requiring sight.)
• Rituals that have a distant target, such as Longsight, are more difficult if you "sense that your target is somewhere where the gods are not looking" (i.e., wizard- or witch-owned property).