Angus's injury from the twin swords artifact is severe and should cause permanent damage. His arms are charred from the inside to the out, and it also ruptures all the mana veins in his arms.
It is known that a ruptured mana vein cannot be healed unless you reach at least sixth grade or above. Even then, it is still hard to make a full recovery. In other words, any fifth grade who got their mana vein ruptured could only become cripple.
According to Angus' knowledge, healing this kind of injury is even more difficult than reviving death. The majority reason for this is that the mana vein is similar to the mana core. It exists and can be felt but doesn't have a physical appearance.
In fact, mana veins are actually very sturdy and couldn't be damaged or even ruptured by normal means. Unless the person is doing something excessive or hit by a sinister attack that is specialized to damage the mana vein, it will be completely intact.
