You have ascended from being an undead king to being a supreme being an overlord, something even beyond the level of an elder lich that pursues magic above all else. However, you are no mere normal Overlord; you gain all the knowledge and abilities of Momonga. Which includes, but is not limited to, all 718 spells that he has memorized; all unique skills that he has gained from the various classes and racial abilities; and every piece of equipment that he has gathered from YGGDRASIL, from cash shop items to mob drops.
Moreover, you gain Four additional abilities.
Dark Wisdom: You’ve attained rare and dangerous knowledge. Your undead mind now is now filled with the knowledge of magic, theory, and artifice. You now possess the ability to learn any magic, regardless of the normal restrictions or limits of your mind and memory. Your undead mind is like a steel trap that no knowledge can escape. This takes effort and study, however, and whether or not it will be worthwhile depends on how interested you are in devoting the time to it. Additionally, so long as you’ve seen a spell cast at least once, you will, with time and effort, be able to puzzle out its workings. Your brilliant mind puzzling out the inner workings of a spell lets you remove restrictions from spells and go about creating brand-new spells that have never been seen before. You’re an unparalleled genius that has no peer when it comes to magic, grasping spells, and rituals that others would require months to grasp in days and hours. Furthermore, you learn a dark ritual that allows you to steal the abilities of others.
The Abyss of Magic: You stared into the Abyss of Magic, but unlike others, you did not flinch away, nor did you go crazy from exposure to eldritch truths. Your reserves of magical energy are heavily bolstered, far beyond what you gained from Supreme Being anyone who could see your magical aura would go blind before seeing a limit to your magic, and the potency of your spells has increased to match your newfound insights into the arcane. You may now amplify your spells, allotting more time, energy, and magical energy to them than they might otherwise be capable of handling, allowing you to gain dramatically increased magical effects and lowering the requirements for spells as a result, such as level cost. Spells such as a spell to summon drinking water can turn into a tsunami that could flood the earth or a flame spell can turn into the might of the sun with enough time and energy, and even your less powerful or obvious magics can be bolstered to a comparable degree. At a base level, the increase in the power of your spell is roughly triple what it originally would be.
Additionally, you are not affected by suppressed emotions and can choose when you suppress them, along with optionally being able to change your appearance from that of a skeleton into that of a human via magic.
You may also optionally gain access to the Great Tomb of Nazarick and all its inhabitants. This Nazarick is in another dimension only accessible to you; you can change how time flows in this place as well as allow people to enter and leave. They are loyal to you and you alone; they can never betray you, as they see you as the last supreme being who stayed with them while no one else did.