The scarf has higher requirements for precision and a more constant overhead than a one-off giant summon.

I mean, there’s a scarf.

And then there’s a scarf

You could make them go “oof” on the summon if you added a requirement that the lava properly flow along the ground and interact with all characters near the event.

I think the better question is “How many polygons do you want and what do you want them to do?”