Having taken into account advise from Moxiethe4th I have reworked the spell.
Mystic Mace: Ob 5, 5 Actions
Origin: Personal
Area of Effect: Caster
Elements: Arcana/Earth
Impetus: Create
Duration: Sustained
Resource Points: 10
Spell creates a Great Mace in the casters hands, Weapon is Dual Nature (Spirit/Natural) and Superior Quality.
The big change over the previous spell is the +2Ob added in for making a superior quality weapon (raised the spell obstacle from 3 to 5). This also makes the spell a little more expensive to purchase, and difficult to learn.
The prior Mystic Mace spell should be downgraded to produce a magic mace that would use RotM Mace stats yet still be a dual nature weapon that matches the sorcerers shade.