Gaven did not teleport it but threw it into another room for separate interrogation.
This is a common interrogation tactic to prevent collusion between parties.
The two pieces of information verify each other, making it easier to distinguish truth from falsehood.
After the Giant Bone King's intentional omission of intelligence, Gaven became more cautious of these Undead Demons, and secular tactics should still be used when necessary.
The Undying Slaughter Divine Power grants absolute control over them, only preventing them from lying but not from hiding the truth.
"This type of golem is called Shadow Steel Golem. It's forged using a special raw material called Shadow Liquid, which tempers and refines the steel. This not only gives the steel a fire resistance far superior to ordinary steel, but also grants them magic immunity, shadow manipulation, and negative energy manipulation abilities."
