Sadly, no, Infernum and Eternity Mode can cause a lot of problems with each other. You can technically have both in a world, but it is unstable, and you have to choose between Eternity Mode changes and Infernum changes. You can, however, get the mod that allows you to play Eternity mode and Calamity Death Mode with no issues, which is what I am doing in this playthrough. I did a personal Infernum playthrough before I started this Eternity Mode series, so that is why I mentioned the comparison between the two boss fights in the description.
wait can infernum can combie with eternity mode
Sadly, no, Infernum and Eternity Mode can cause a lot of problems with each other. You can technically have both in a world, but it is unstable, and you have to choose between Eternity Mode changes and Infernum changes. You can, however, get the mod that allows you to play Eternity mode and Calamity Death Mode with no issues, which is what I am doing in this playthrough. I did a personal Infernum playthrough before I started this Eternity Mode series, so that is why I mentioned the comparison between the two boss fights in the description.