Yellow swarms are groups of insect-like creatures. They must stay in close proximity to one another, or they lose their ability to remain on this plane of existence. They look like a small cloud of yellow locusts until you get close enough to see that they are transparent and oddly configured, with asymmetrical bodies that have seven legs and five wings.   Hunger for Brain Fluids. Yellow swarms feed on various chemicals in the brains and spines of living creatures. Defending against this hunger is tough because a yellow swarm is always fading in and out of reality. Yellow swarms often linger near interdimensional gates or other access points, so the presence of a swarm is a good indicator that a gate is nearby.