
Originally Posted by
Comun
It's more like they were picking from pre-existing options. What happened there is that Zelretch was browsing timelines and found FsF, but he saw that if left unattended, FsF is the "Jester wins" timeline, so he went "Spider, don't want that" and started choosing a mage to intervene.
But Caubac stops him and recommends a non-mage intruder, presumably because Zelretch's choice of mage would cause the "Francesca wins" timeline, which inconveniences him perfectly because Francesca's Grail wish is to steal Caubac's treasure.
Caubac selected fake Ayaka from Zelretch's book so it makes more sense to me that she was fully pre-existing. Her semi-copying Sajou Ayaka's looks could have been on Caubac though. Caubac is also more directly involved with creating the phone line between Dumas and Waver to prevent Ishtar as well. Zel is here basically just watching Caubac do his moves.