As protection from energy, except lasting 1 day/level instead of 10 minutes per level and that the spell only protects against acid and fire damage (and while energy protection remains, the item is also completely waterproof).
The target’s bones or exoskeleton shiver and splinter, dealing 1d6 points of damage per caster level (maximum 15d6) to the target, who is also exhausted for 1 minute per caster level from the pain and exertion of the transformation.
Cut yourself and swear an oath of retribution on your own blood. Any attack, save, or check related to the oath grants you a morale bonus to that roll equal to the number of hit points of damage you sacrificed divided by 5.
A blast of hellfire deals 1d6 damage per caster level (maximum 15d6) to the target (half fire damage half unholy damage.) If a creature is killed by this damage it must make a Will save or be damned to Hell.
Eviscerates the target, drawing forth his life essence as well as his internal organs, inflicting 1d6 hit points of damage per caster level (maximum 20d6). If this kills the target, the spell pulls his organs into a set of 4 canopic jars and seals them; creating an Osirion mummy 1d4 rounds later.
Endzeitgeist says: "Legendary Classes: Covenant Magic is worth every cent thrice. At least. This is the new gold-standard for class-design against which all other classes will be judged. My final verdict would be 6 stars, if I only could – hence, 5 stars + seal of approval and a high chance that this will feature on my Top Ten of 2013-list.