Oliver had decided to believe Val's explanation, but he wouldn't feel at ease unless he had confirmed the existence of the mentioned artifact with his own eyes.
Val had stored the [Upgradable Cursed Sword] in the pocket dimension of the [Void Orb] before he lost consciousness. He could show it to Oliver at any time and be done with this investigation, however, he hesitated.
Oliver's question was simple but it wasn't easy to answer.
Firstly, what Val had said about [Voidslayer] was a lie, and if Oliver had the ability to determine the true worth and effect of a cursed artifact, he would catch on to his lie, and the situation, which had just calmed down, would immediately become tense.
Secondly, Voidslayer was an upgradable level-2 artifact with a spirit. If Oliver recognized its true value, who was to say he wouldn't covet it? It was much safer to keep its existence hidden until he had gained the strength to protect it.
