Cassian actively try to learn spells. Most of his mastery progress comes from his own effort and practice. He has to start from scratch, just like a first-year student, learning everything from the very beginning. That is why there is some delay in his spell progression.
On top of that, he also needs to catch up on magical history and theory in order to fulfill his role as a teacher.
Lumos Noctis: Extinguishes all light in the area, plunging it into total darkness.
Lumos Spectaculum: Projects detailed moving illusions made of light (figures, scenes, etc).
Cinis Amissa: Summons the ash of a past flame, revealing what was last burned in that place, useful for uncovering lost scrolls or evidence. (Can only be used once per burned evidence.)
Pyroclave: Stores fire within objects, runes, or text, released under specific conditions.
MAX Mastery means Cassian has passed the threshold of the Interface and was awarded with Ancient Variants. He can now cast those spells wandlessly and non-verbally, including the Ancient Variants, even if he hasn’t reached MAX Mastery on the ancient variants themselves.
This list will be updated as more spells and Ancient Variants are revealed.