As in underworld essence? Or is it just any essence?
Either way, update 0.5.7 should've fixed that
Honestly, just try removing mods one by one to figure it out. Start with the most obvious offender, lets say... imkSushi as an example. Work your way through the mods from there, that's really the best way to go about it. If you have cheat sheet/HERO's mod use that on a character to make testing faster and easier
EDIT: Wait wait wait, I think I might've figured out my issue. Might be because I'm not using the 64 Bit version of tModLoader, which would be an absolutely insane if that was really the problem, but it might be. I'm gonna test this and make sure, give me a while to install 64 Bit to make sure
Edit of the Edit: Figured out my issue with launching the mod! Apparently it only wants to work on the 64 Bit version of tModLoader, which is understandable considering that 64 Bit is better. Just didn't bother to get it until now, time to see what this mod has to offer.