What is the relevance of the creature that emerged from the egg?

At the end of the third season, Faustus Blackwood uses the time egg as part of a ritual to call forth the eldritch terrors, which was of course successful, as we see in the following season. We then see that the egg has hatched, and some sort of creature has emerged. It certainly seems that this creature will have some role to play.

However, when we see the eldritch terrors, they seem to be ancient entities, and none of them seems likely to have hatched from an egg, nor does any resemble the creature that we saw in the third season. In fact, many are abstract, such as a pool of darkness or an alternate reality.

So what was the creature that emerged from the egg, and what was its connection with the terrors that came to Greendale in the fourth season?