update: i got it to work but for some reason you need to have 2 or more in the same slot for the duel to actually begin

Eater of Worlds is a little bit buggy since it travels quickly and can get outside of the 'start duel' detection range in the middle of the 'start duel' animation. I'll include a fix for this in the next update.

I was so confused. I'm on Infernum so I assumed it was related, but it had already worked with King Slime and didn't change for the Eye or Eater once I disabled it.

Tested out staying close to the boss and I'm glad to see it works.
Really great mod, but man do I hate how evil some of those combos are.

i had that issue and i solved it by holding more than one invitation out, i think it happens to me when i switch to a different item (or run out of invitations) while the animation is playing