The boss of the second strata was a Mummy King. Unlike the Iron Golems guarding it, the Mummy King is using mental manipulation and something related to mana dispersal, making mana useless most of the time. It would be dangerous and totally disastrous if the one fighting it was someone who uses magic. But for someone who barely have any mana in their body and is seemingly immune to mental attacks due to the same reason above, the Mummy King is not even a threat to Elaina.
Because it is more focused on using those attacks to incapacitate anyone, when against someone who is immune to all, in short, the boss was just nothing for Elaina and she easily killed it before it has even a chance to fight back.
"Haaah...that was a quick work but I am feeling tired already," Elaina said to herself as she activates the teleportation circle which will allow her to teleport directly in here if she wanted to.