Talk:Overlord Volume 9/@comment-27012362-20151007163742/@comment-27023992-20151007191736

The confusion comes from here: Overlord Volume 1 Chapter 4

"The Death Knight was another mystery While inside YGGDRASIL, summoned Magical Beings expire unless they were called forth by special summoning methods. This Death Knight wasn’t summoned with such methods. It ought to have expired, but it didn’t."

and Overlord Volume 1 Chapter 6 Epilogue

"As Ainz thought about that, the sound of metal clanging rose.Looking at the source, he found a long sword on the floor. The Death Knight holding the sword was gone. It was summoned not long ago.“... It disappears after a period of time if it was summoned using normal methods… Since the sword from this world was left on the ground, it wouldn’t linger if equipment were used as a medium to link to the otherworld. Hence, they long for this world if it was summoned using their corpse and won’t disappear? If there were a huge number of corpse, it can be used to strengthen Nazarick."