Since there is (currently) only one land that ice is available in, and it's a bit of a... hot commodity, what if there were a winter event that introduces a temporary upsurge in ice availability? In this case, transforming the Firebogs into Icebogs for a limited time. Jellisacs appear to be largely fluid, so a limited amount of them would be affected by the frost and temporarily frozen into ice nodes. However, not enough as to entirely eliminate jellisacs from the overworld for that period; it would make sense for some jellisacs to be resilient enough to withstand the low temperature and remain viable during the event.
Thoughts?