The descending tunnel led him down, but not without some tension. Who or what was this monster? How, without being able to kill it, did they transform it into a mummy? How and why? Wasn't the cure worse than the disease, creating an eternal and powerful being?
According to Norse mythology, Loki was a god associated with betrayal, deceit, and subterfuge. If the game developers had based this plot on that, it was clear Ikky couldn't trust this guy, but his instincts kept telling him there was no danger ahead.
The behavior of those proto-humans had no explanation for the Spaniard; either they were holes in the plot, or there was still a lot of the plot we couldn't discern.