I have received a reply from Sannse of the Fandom staff.
"Hello Antvasima
This is a tricky line. We allow a lot if the gore is fictional. For example, we have a Saw Wiki and a Final Destination Wiki, both of which are very gory. However, we have previously closed a couple of Japanese Manga wikis that were very violent. The difference was largely that the extreme gore and violence was also sexual. I also recently deleted a story that was very gory and violent and used a children's character as the victim (MLP). Real gore is definitely not allowed.
The content rating scale really only covers sexual content. But there is a line with gore, and I would say detailed torture and murder of children crosses it. Especially if it has any sexual elements. Basically, if it's gory and fictional it's okay, until it becomes torture po rn or shock content.
I can't speak to the specific case, as I don't know the content. But if it gets explicit with violence against children, it probably crosses the line.
I hope that helps
Regards,
-- Sannse"