The mystery work embed is only formatted properly for mystery works belonging to the Null Collection.
Test using this work which does not belong to the null collection and this work that belongs to the null collection.
I made an assumption that all mystery works belong to the null collection which is why this error happened in the first place.
The specific line should be this

Some Ao3 stories need you to be logged in before you can read those stories. Those stories have a 🔒 in the story name.
Summarium should either:

• Create a bot account on ao3 just for checking those stories (I do not like this)
  or
• Respond with an embed telling the user they need to log in to view this story

Summarium is ignoring some SpaceBattles story links for no reason. Summarium has to be forced to look at the link (with the use of a slash command) before it works.

Summarium was returning an error embed for stories that did not require login.
Added a print statement in AO3_Embed and got this:

"Error with A03 Story -> invalid literal for int() with base 10: '130,331'"