D&D 5E Volo doesn't tell me what some of these things actually are.

[gyor]

Ignore the picture, that not what Firbolgs have ever looked like in the realms. Firbolgs are huge red headed human looking beings.

 

[Sword of Spirit]

If I recall, there actually are descriptions of some creatures...just not of others.

 

[Mecheon]

Ignore the picture, that not what Firbolgs have ever looked like in the realms. Firbolgs are huge red headed human looking beings.

The problem is no one cared about Firbolgs previously when they were "A giant but at a different height, more friendly, and more celtic"

This at least gives them their own niche which heck knows they've needed for a while.

(Also I found some other unused concept art for Firbolgs and can confirm it works)