What unique Blades are not available through random drop from generic Cores Crystals?

Solution 1:

For the sake of completion, I'm going to include the ones you mentioned. There are 8 in total.

Roc - Roc's Core Crystal - gained via story

• Wulfric - Beastly Core Crystal - gained via story

• Kasandra - Lucky Core Crystal - gained via salvaging at the salvage point in Chansagh Wastes until a Gluttonous Marrin spawns, which would drop this crystal

• Herald - Sealed Core Crystal - gained via feeding "blood-related" items to the Shrine of Sealing in Theosoir, Tantal

• Sheba - Inherited Core Crystal - gained via spending 500k at the shop in Gormott

• Vess - Vess's Core Crystal - gained by doing Vess' sidequest ("Tranquility") in Gormott

• Praxis - Praxis's Core Crystal - gained by doing the Crystal Clear side quest

• Theory - Theory's Core Crystal - gained by doing the Blade-Sharp Memory side quest (this is related to Praxis)

In fact, one thing worth mentioning is that all of these Blades are available through a common core crystal drop if you release them. This is a strategy that was used to trade Blades before Overdrive Protocol farming was possible.