Overseer

Iggy
Iggy is the name given to the yellow Overseer you meet at the beginning of the game. He acts as the very basic tutorial and, if you follow him, guides you to Looks to the Moon.

WARNING (and spoilers)

If you kill Moon (eat all her neurons) Iggy will leave you.

Signs (this is kind of a spoiler)
As well as teaching the player the controls, the yellow guide will point to things and put a symbol next to the arrow. The symbols are (based on videos of people playing this game):

An upside-down 2 with 2 lines above it: This symbol seems to mean "there is a predator that way" when the yellow guide points to an edge of the screen or to a tunnel, and "this wants to eat you" when the yellow guide points to something. This symbol will change between yellow (the color that the symbols are normally) and red (probably to make it clear that it's dangerous).

A bat outline: "There is food that way".

There are also images shown in octagons that are not used to show where stuff is, but the meaning and purpose of these is really unclear.

Blue Overseers
Blue Overseers appear after a while, like the yellow one. Blue Overseers can be seen interacting with each other by connecting their arms/tendrils with each other which will cause little sparks. Occasionally, a careless blue Overseer (besides the guide) can be killed by a curious scavenger that throws spears or Rubbish at it.