The fluid consists mostly of blood, albeit of a different chemical make-up than normal blood which likely causes the darker shade. This is an alien planet, after all- there are going to be differences that don't necessarily fit into one's expectations. Separated, at least one of the alien compounds could be identified as a type of toxin, and prolonged or unprotected exposure to it would cause a similar reaction to the sickness that affected people who worked too long near the crack in the wall. It could be gleaned that the invading creatures have been mutated by whatever poison is affecting the world outside the barrier.

There is no specific energy to it, as it's dead and mostly inactive, and it does not feel at all like the barrier or crystals.