The lake of magma was the only thing illuminating the environment, and while it was enough to cross it, climbing the walls would be dangerous. A single mistake and the carriage might roll down the slope and fall on the lake.
"Don't worry about that. With my current strength, I can stop the carriage if something happens," Zane said and then began to lift the whole vehicle with everyone inside and using a single arm.
They got some extra things like materials and stuff, so Zane's strength certainly was something else. Regardless, they crossed the portal since they couldn't rest in such a situation without Yolanda's help, and sleeping while she worked would be a bit too much.