Surtr Meets Emerald
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Although I used a Skill to transform into a humanoid "Draconid" or "Dragonoid" shape, however anybody wants to call this semi-humanoid form a dragon can take which shares a few of their draconic characteristics while looking like the humanoid races of Yggdrasil, it was also possible to undergo this change through the usage of Polymorph Magic or Draconic Techniques.
Even when he's very strong at Rank 9, Emerald doesn't seem as connected with the Draconic Records to draw power out of them, sadly. He possesses no such thing as a System for Skills, so the best thing we can do is teach him the "Humanoid Form" Spell of the Polymorph Magic, sometimes also referred to as Transformation Magic or Shapeshifting Magic.
It is a branch of Life and Nature Attribute Magic that delves into the transformation of a person's body form. I know only a bit of it thanks to Pekora's teachings, but this spell alone should do the trick.