Mountainside Battle
Christopher wasn't particularly surprised by the difficulty of the mountain chain, or how the difficulty was set.
This is because the higher one went, the colder it became, and the denser the Mana was. As such, the higher one went, the stronger the creatures they could encounter would be.
The tiger he killed at the base of the mountain he was climbing was at the bottom of the food chain in this place, and the difficulty gradually increased as he climbed.
Moreover, the battles were hardly ever straightforward. Sometimes he'd fight beasts and creatures that required head-on collisions. However, beyond that, most of the things he fought could easily be considered to be nightmare fuel.
A clear example of this was when he had reached the 5-kilometer mark on the mountain he was climbing.