The Goo people are a rather mysterious race of Abominations that we know not much about at this moment.
The first appearance of that race was in Episode 14: The Goo the Bad and the Ugly were a green specimen fought alongside a Formian and seem to be included in a deal with the Rajis. Both the Goo guy and the Formian were killed shortly after they were introduced.
In Episode 32 Why are we talking to these Guys, two Goo people appeared. One green and the other brown, the voices and the different coloration may hint at different genders. These Goo people may have had a deal with Lady Majunala to scout out the Northern Terminus.
The one eye at the centre of their body is powerful enough to count as an Eldritch eye for Teleportation, despite they seem to have no Eye-based powers, like the other times the team acquired Eldritch Eyes from creatures.
They have the base-stats of a Manticore (which explains the 6 ranged spike attacks and the Goo wings) but also have a "Bullshit defense" which allow them to subtract 2 damage per die rolled on any attack against them. It's not known if this is in any way avoidable.
Surprisingly, despite their appearance and being made out of Goo, they can be sneak attacked and critted, because some parts of the Goo they are made of are vital to them.
They are also not "bloodied", instead they acquire the status "gooied" if they go beyond half hit points.
Somebody also wrote a fanfiction about them called GOOOOOO.