Creatures you have sacrificed may appear on the Astral Plane. Possibly, give the player a means of summoning them there as pets.

In variants that have element-specific mages, the message for a sacrificed corpse disappearing is different if you are playing as one:

• Ice Mage: “The corpse is swept away in a blast of frost!”
• Acid Mage: “The corpse dissolves into thin air!”
• Fire Mages either use a standard burst of flame, or a message suggesting more powerful flame.

For Infidels, sacrifices of baby monsters (those with a “baby” in their name) are treated as though the monster had a higher difficulty than it actually does, as a reward for sacrificing babies.

Sacrificing the Eye of Vecna zeroes any alignment abuse you have accumulated.

Several elaborations on a system for more reliable (and less tedious) gifts from altars:

1. Your god will always give you a gift on the first sacrifice from a given coaligned altar (not if attempting to convert an altar). But after that, they will not give you any more gifts on that altar no matter how much you sacrifice. (Other sacrifice effects will still happen as if you failed the die roll for a gift.) This eliminates all the tedium associated with altar camping for gifts (though not all altar camping in general), but is a significant change since getting one corpse to an altar is much easier than getting multiple ones, and streamlining the game to this extent may be undesirable.
2. As above, but the gift will only be given for the first monster whose difficulty is above a certain threshold (possibly partially dependent on depth, and also with some random factor). Thus, if you sacrifice and get no artifact, you know you have to try a harder monster.
3. The total difficulty of monsters sacrificed is accumulated; the first sacrifice to put you over some threshold (say, 30 cumulative difficulty) is guaranteed to give you a gift. The totaling may or may not be per-altar.
4. Your god has a set list of rewards, each of which is tied to some monster difficulty level. Some of these rewards are artifact gifts; others may be things like luck. You only get a gift when you sacrifice a monster of the requisite difficulty, and thereafter monsters of equal or lesser difficulty to that are ignored by the god for reward purposes (they may still be used for mollifying and decreasing prayer timeout). If you make a sacrifice that earns you multiple rewards at once, you either get them all at once or you get the biggest reward and the smaller ones on subsequent sacrifices. This would enable game developers to fix a number of artifact gifts (say, 3), by encoding that many rewards for them. This system might have problems in games with no deep usable altars where it is harder to get randomly generated difficult monsters.
5. Variation of the above: at the beginning of the game, three random monster difficulties are chosen (with some limiting on ranges). Sacrificing a monster of a difficulty above any of these thresholds automatically gives you a sacrifice gift and removes the highest remaining threshold you met.

Cavepeople can safely sacrifice same-race monsters to “give them to the ancestors”, but only if the monster wasn’t killed by the player.

Sacrificing a lamb should guarantee a gift, or at least have a very high sacrifice value.

A chaotic Cartomancer who performs a same-race sacrifice gets not a peaceful Juiblex or Yeenoghu, but a card of summon Juiblex or Yeenoghu.

In variants where you can gamble away, sell, or otherwise lose your soul: a character who has lost their soul will get no more help from their god (until they manage to recover it). Sacrifices will be accepted but will never get rewarded with a gift; otherwise successful prayers will fail to give you shimmering-light invincibility, will go unanswered, and will give you no message as to the pleasedness of your god, and possibly you lose your divine protection as well.

Define gods as having an associated holy animal (e.g. crocodiles are Offler’s). If you sacrifice that type of animal to that god, it immediately angers that god.

Priest characters can sacrifice gold at a coaligned altar for identical benefits as they would get from donating to a priest. The altar does not have to be attended.

You can offer gold on a coaligned altar as well as giving it to a priest. This gives you a different, weaker, variety of benefits if there is no priest present (and the same ones if there is a priest present). When you do donate to a priest, they offer the gold themselves in a burst of light (which deletes the gold, preventing you from killing them or stealing to recoup it).

Gods should react in some way when the corpse of one of their own priests is sacrificed. They currently don’t (unless it’s a same-race sacrifice) and this is weird.

Fuzz the effective difficulty of monsters sacrificed, so that you can’t trivially count up and calculate how much more you need to sacrifice.

Aligned altars can generate in Gehennom, and standing on a coaligned altar in Gehennom is the only way to contact your god (via prayer or sacrifice). If the altar is crossaligned, you can try to convert it, but Moloch may seize control during the process and turn it into an altar to Moloch. Molochian altars in Gehennom are very difficult or outright impossible to convert.

Track, and report at the end of the game in the dumplog or xlogfile, how many times the player prayed and sacrificed.

Chaotic same-race sacrifice demon summoning causes the demon to give you a nice item or some gold when they appear.

Burnt offerings: via some mechanism, you get the corpse smoldering on the altar. When sacrificed, it is treated as higher difficulty.

Most corpses have sharply decreased amounts of nutrition (from the current values). They may also be too mangled to be good for a sacrifice, randomly based on their object ID. Their intrinsic-conveying chances are unchanged, though.

Priests can sacrifice corpses anywhere, with no need for an altar, except in Gehennom. (This should be strictly worse than altar sacrifice - maybe it only reduces prayer timeout, by less than it would normally, and can’t result in gifts.)