I thought that it would be interesting to have a place specifically designated for us to discussed which thematic and character ideas have been recycled from older iterations of the Nasuverse and incorporated in Neo Type-Moon / Post-Fate Type-Moon.
(you may also mention ideas that you found in works from the other authors not named Nasu that they incorporated into their TM works).
For example:
1- Musashi's Mystic eyes being previously shown in the bomber from KnK.
2- Goetia being an a tie-in to the "Ancient I" (i also think that Nasu took a lot of ideas from the Dark Six that was described as a "System" made up of various entities and incorporated some of those ideas into Goetia. lets not bring up the Six Sisters into this either i suppose).
3- Achilles' immortality is oddly similar to Astaroth's ability in Higashide's previous work called "Tokyo Babel".