Realm Expansion (1)
While harnessing the power of another realm, the user is exposed to the vulnerabilities and dangers inherent to that realm. In the case of the underworld, they might be susceptible to the influence of vengeful spirits or demonic entities.
[Realm Expansion] is not without its limitations and costs. The power drawn from another realm is not infinite, and excessive use can weaken the connection between realms or even lead to unintended consequences. Additionally, there may be moral or ethical dilemmas associated with siphoning the power of other realms.
Proficiency in [Realm Expansion] requires considerable mastery, both in the manipulation of dimensional rifts and in the management of the acquired power. Inexpert use of the skill can lead to catastrophic consequences or a loss of control over the borrowed powers.
For this reason, Mammon used to be called:
"The Strongest Demon Lord. I think it's about time I take that title back."