Kelleris said:So I'd actually say that my point, which was that conjuration spells generate a real stuff that can be expected to have real-stuff-like effects - like a layer of grease being churned into hard-to-manage goop by a swarm - is supported by these cases. Presumably plenty of grease leaves the spell area after it's cast, just not enough to generate the grease spell's effect. I don't see why the grease wouldn't act like grease (get smeared all over the place and making everything slippery, including making more than just one doesn't-actually-exist-as-a-defined-unit "bottom row of centipedes" so) as long as the swarm is in the spell's area of effect.
Precisely.
You have finally looped back around to my main point.
"as long as the swarm is in the spell's area of effect"
A 10 foot square of Grease is NOT a cube. It does not affect everything above it.
Since the non-flying swarm is shapeable and can climb on itself and its prey, it does not have to remain in the area of effect of the spell, especially if there is prey to hang onto.
And, any creature that touches the grease is not affected by the spell effects of the grease once they leave the area of effect (just like all of the Fog and Cloud spells). There might be bits and pieces attached to the creature, but they are minute and irrelevant to game mechanics. Just like a dispersed Fog spell.