Having personally witnessed Serlun's death, Roy could not help but feel completely relieved. A Lower Demon like him had actually managed to trick an Upper Demon to death—it sounded unbelievable even when spoken aloud.
Of course, this outcome had been the result of many factors: the war itself, Serlun's greed, the infighting among demons, and so on. But no matter what, Roy had made reasonable use of all those factors, combining them cleverly to achieve the result he wanted. Since a Lower Demon could not match an Upper Demon in strength, he could only rely on intelligence.
The moment Serlun was banished, the Demon Contract became invalid. At the same time, a name suddenly appeared in Roy's mind.
Oseric... Serlun!
Needless to say, this was part of that fellow Serlun's Demon True Name. Because Serlun, as the summoner, had died, the Demon Contract judged him unable to fulfill the contract and compensated Roy, the summoned party.
According to the rules of a Demon Contract, if the summoner died, the demon could claim the other party's soul. However, this Demon Contract had been made between demons in another world. Both their souls were protected by the Ouroboros Mark, so neither could seize the other's soul. In the end, Roy could only receive compensation in the form of learning part of Serlun's true name.
It was only part of his true name, not the whole thing, so it was not all that useful in reality. Unless Roy could use Demon Contracts to trick Serlun several more times, perhaps he could piece together Serlun's Demon True Name. But no matter how foolish Serlun was, he would not possibly give him another chance to do that.
Come to think of it, Roy did not really understand how Demon True Names were meant to be