This isn’t gunk at all, rather, it’s BLOOD. Well, it was blood, though it has since been used in a RITUAL. Now it serves as part of whatever it is the caster wanted done.

This SPELLWORK is rather crude though, someone was either in a hurry or not very experienced with making entirely physical SPELLS. At least they got the proper multi-use CATALYST. Sadly they made a mistake in their haste, leaving the BUCKET OF BLOOD here, which most definitely is the blood used for this very RITUAL.  It could prove useful.