Teleport vortex, a monster which moves around the level sucking up items into its inventory; items in its inventory are periodically teleported randomly around the level. If it engulfs the hero, it will do the same.

Fire vortices uniquely among whirly engulfers don’t make your lamp or candle go out when they engulf you; they keep it ignited. In fact, they might ignite any candles you happen to be carrying in main inventory.

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

Vortices, or possibly all whirly monsters, scatter items to different squares when they pass over them (using the throwing code, so items may shatter and creatures may be hit by them). Possibly only objects under a certain weight.

More evilly, they could be able to scatter unequipped items from your inventory when they engulf you.