By the time we get Eridan's official intro page, he and Feferi have already been introduced by name, and we have a basic understanding of how their relationship works, what with the slaying of lususes and the feeding of Gl'bgolyb.
The narrative acknowledges that it is a thing that all characters get an intro page in their room.
======> There's not too much I find interesting about this page, except Eridan's "penchant for mass murder" and this passage:
You also like MAGIC, even though you know it to be FAKE. Like a made up friend, the way wizards are. Made up make believe FAKEY FAKEY FAKES. It's still fun though.
Another adamant refutation of magic by the narration. I'm not sure what all these mentions are building to. Also, I get a weirdly Harry Potter vibe from Eridan. There seem to be a lot of Harry Potter references linked to him, and I don't know where all that is going.