A special container that can hold the invocation items, and only the invocation items. Has bag-of-holding-like properties (or else is an artifact bag of holding). It appears in some hard to reach place in the dungeon.

Bags of holding should cost 500 zorkmids; this makes them trivially price-identifiable, but it’s not hard to identify one in a shop anyways.

A greased bag of holding prevents corpses inside it from spoiling like an icebox will.

Your god may give you useful non-artifact items as sacrifice gifts, such as a stethoscope or bag of holding, so long as you aren’t carrying one of them already.

A slightly more advanced system that wouldn’t require carrying a bunch of items to avoid getting duplicates would be to track the last time you picked up or put down each type of object, and if you have never touched one or it’s been a sufficiently long time, you are eligible to get that item as a gift.

Canceling magical armor not only sets it to +0 but turns it into a nonmagical counterpart, which consists of new items such as “faded cloak”, “faded boots” etc. This would probably also rename “faded pall” to avoid confusion.

When a wand of cancellation is placed into a bag of holding, rather than blowing it up, it instead uses up (all of?) the wand’s charges and turns the bag into a sack.

For consistency, bags of holding should probably turn into sacks when zapped with cancellation as well.

This forces potentially interesting choices on cursed bags of holding in bones files, since now cancellation cannot safely be used to loot all the contents and get the bag too.

Bags of holding give a flat reduction in weight (proposed amount is 150 aum) and only apply their usual halving or quartering to any weight in excess of that. This makes it beneficial to find and carry multiple bags of holding.

Eating a bag of holding confers temporary intrinsic hunger, and eating a bag of tricks confers temporary intrinsic aggravate monster.

Exploding a bag of holding gives you a respectable amount of experience points (because you certainly learned something from that experience, and it would be hilarious to accidentally level up by doing this.)

Putting a wand of cancellation into a bag of holding does not blow up the bag at all; it cancels the wand (as in NetHack4) and additionally “cancels” the bag by turning it into an uncursed sack (which does not normally happen when zapping magical bags with cancellation).

Not specified whether putting in a bag of tricks or second bag of holding would also have this effect, or whether it would still blow up the bag.

Blowing up a bag of holding doesn’t destroy any of the items; it just destroys the bag.

When a bag of holding explodes, each item inside has a 1/13 chance of being destroyed and a 12/13 chance of being scattered (using the same code that scatters drawbridge chains). Note that scattered fragile items such as potions are liable to break by crashing into things.

You can apply a cursed bag of holding (or possibly empty bag of tricks) at a ghost to capture a ghost, which can then be used to recharge a wand of undead turning.

Placing bag-of-holding-explosion-causing items into a bag of holding blows up the item that is trying to be placed inside, but does not harm the bag itself. If the item causing the explosion is a second bag of holding, its contents end up inside the outer bag.

Opening a cursed bag of holding does not tell you what has disappeared, or it just says “Things have disappeared from the bag!” without describing them.