Thanks for the feedback so far. Addressing some of the suggestions on specific liquids:

Sunslag: This is a good idea, I had missed the link between it and, uh, big robots. I will revise this. I like gel as a liquid for more advanced/less mechanical entities, but sunslag would make sense as a third tier for robots: oil for basic/mechanical ones, gel for more advanced creations, and sunslag for true wonders of the Eaters like baetyls, galgals and chrome pyramids. Will probably move Yd to wine or cider, although that's not perfect either IMO.

Warm Static: Static as liquid for the Chimes makes sense at first blush since there's plenty of it around, but most of it is diluted (similar issue to algae). Pure static can be reliably sourced from Zero Jells, but they're a tough enemy that can be annoying and risky to fight due to the random effects thing. There's probably something to be said for something a bit easier, maybe primordial soup.

Putresence: This was a tough one but I kind of like it for Gyre Wights. As I understand the lore, wights are regular humanoids who worship the Girsh and use various methods to try and become more like them. I thought about green goo or black ooze, but these are both closely associated with Agolgot alone, and I found it hard to imagine them being ingested regularly even as a religious thing. Some of them used blood in the past, but the mod already expands the use of blood extensively. My perception from their dialogue is that they have a rather proudly "perverse", nihilistic worldview and are also fond of symbolism, so ingesting Putresence (which is basically vomit and the like) seemed to fit. I hadn't considered specific liquids for wight types - that's not a bad idea and would find a use for a few more, but I wonder if it would overcomplicate it too much. Will think about it.

As a general design note, I tried to make sure that the liquid was always something valuable to the creature. At one point I had lava for magma crabs and convalessence for trolls, but it seemed odd to be offering a liquid to a creature when they're basically sitting in a pool of it.