Archos' seat seemed empty. Seemed being the operative word. He was actually there, in the form of a tiny spider, looking to any who actually noticed him as just being one of the little spiders you see every so often in life. It was also useful as he doubted his real form

In this state, he was just watching and listening as the others turned up. Most - those who hadn't made an effort to hide and avoid people learning of them - he recognised, their faces, names and voices registering somewhere in the vast archives of his mind. He then makes the decision to make his presence known, his voice echoing in the minds of the others.

So you all are the others these gods have brought in. Interesting. I am Archos.

Spoiler
Show

Knowledge (religion) check about these gods: (1d20+53)[67]
Lore roll for the same: (1d20+33)[41]

Archos also has Mindsight, out to 120ft, and True Seeing, if that gives him anything extra about the area we're in.