Pale jelly, a j or j that has an engulf attack that causes illness and a difficulty rating appropriate to that. Some may be found on Juiblex’s level.

Shambling horrors can always engulf adjacent monsters (rather than it only happening some of the time) and add their special attacks. Though this works only for the shambler that engulfed the monster, it does not propagate to all the other ones.

The message for getting engulfed should distinguish between monsters that swallow you whole / have solid bodies versus ones that aren’t. For these monsters it should print “The purple worm swallows you whole!” instead of “engulfs you!”

When you are riding and get engulfed, you should be “ripped from your mount”, because currently this behaves weirdly - you end up still riding your mount inside the engulfer, your steed is not adversely affected, and if you dismount you “float down” and the steed magically pops outside the engulfer. The size of your steed also doesn’t matter, so it also doesn’t make much sense if it’s something huge like a dragon.

If you controlled teleport to the same spot as an engulfing monster, there is a chance of teleporting inside it and being instantly engulfed instead of landing somewhere else.

When you read a scroll of fire inside an engulfing monster, the fire explosion hits it 8 or 9 times instead of just once.

If a digesting engulfer eats an e monster that explodes (either actively or upon death) or potentially any monster with an explosion attack, the monster is assumed to explode inside the engulfer, who takes double damage from that attack (or 8 times damage, if the explosion is considered to have hit them 8 times) and is stunned and immobilized for a few turns, unless they resisted the explosion’s damage type in which case they only suffer that for 1 turn.

This should also extend to other explosions inside engulfers (most of these would be player-created: e.g. reading a scroll of fire or breaking a wand while engulfed).

When you’re in an engulfer with a digestion attack, the digestion attack hits every turn regardless of the monster’s actual speed. This is because most digesting engulfers are slow, and it takes way too long for their digestion to become actually threatening.

Monster which is a shapeshifter, but regardless of what form it takes it always has an engulf attack. This is because it’s actually a variety of mimic in its normal form.

Give giant mimics an engulf digest attack; they’re certainly large enough to swallow you in one gulp.

Flying creatures have a chance to auto-evade engulfing by flying out of range of the engulfer’s attack. Maybe only if the engulfer isn’t also flying.

The spell of knock cannot be used to escape from an engulfer (the wand of opening, however, still can). Casting knock into an engulfer produces the message “You knock on the inside of [monster], but nothing seems to happen.”

Using digging to escape from an engulfer no longer leaves it teetering on the brink of death at 1 HP. Instead it cuts the engulfer’s HP in half. For unsolid or amorphous engulfers (e.g. Juiblex), it does even less damage than that. It still lets you escape in all cases though.

If you are mostly surrounded by puddings, they will merge together all at once and engulf you. This is a delayed instadeath in several distinct stages:

1. The puddings tower over you and merge together, preventing escape. You are engulfed, but you can still do things like attack or zap a wand of opening.
2. One or two turns later, your arms and legs are grabbed. You can no longer use most items but may still be able to cast spells and read scrolls.
3. The pudding spreads over the rest of your body. You can’t speak or do things that require speaking, though prayer is still possible.
4. The pudding is forced down your throat, dissolving you from the inside. This either kills you instantly or gives you a few more turns to live if you have magical breathing.

Whirly engulfing monsters have a random chance of causing dizziness (stunning) every turn you are engulfed.

Green slimes have an engulfing attack that guarantees to start the sliming process (assuming the player isn’t unchanging, on fire, etc).

Moving right into an engulfer with the ‘m’ prefix automatically engulfs you.

Being engulfed by a solid monster makes you blind unless you are carrying a light source, because it’s dark in their stomach.

A digging ray shot into amorphous engulfers (such as green slimes or gelatinous cubes in some variants) splits them instead of reducing their HP to 1. This automatically makes you not engulfed anymore. (Does not change the effect on things like purple worms. Not specified what should happen with unsolid engulfers like vortices and air elementals.)

Escape as its own key should be used as an actual escape command, so you can do things like try to get out of pits and engulfers with it.