Sunny was more of a copycat than an actual sorcerer. Most of his repertoire consisted of recreating the weaves of various enchantments he had gleaned from his own Memories, not creating those of his own.
Of course, even that was already a stunning achievement. Armed with nothing but his intelligence and a bit of intuition granted to him by Blood Weave — as well as the ability to see weaves, in the first place — he taught himself the most fundamental principles of sorcery. The wondrous sorcery of the Demon of Fate, which very few beings had ever been able to wield.
At this point, Sunny had barely taken the first step away from blindly copying the spellweaves, tentatively trying to disassemble and modify them to serve his whims. The Siege Souvenir, a unique Memory he had created to slay the Fallen Titan Goliath, was the result of these attempts.
