Are cards that state:

When purchased, place this card in your play area.

considered to "in your deck" for the purpose of the 'minimum 15 cards' restriction on the Overloard deck limit size?

(If I recall they are not considered to be in your deck for the purpose of adding higher level cards to the deck)

I think Zaltyre once noticed, that this detail was strangely only talked about in a news article about manor of ravens.

Quote

Once you purchase the Call of the Ravens card, it’s always available to you. It's never shuffled into your Overlord deck, and doesn't count toward your Overlord deck total, meaning you can use it at any time.

The article can be found here: https://www.fantasyflightgames.com/en/news/2014/7/28/dark-and-unknown-magic/

As per uFAQ, these cards do not count towards the Overlord's deck size or towards his ability to purchase higher level cards.

Ahh there it is. Thanks to you both.

"Summon cards do not count towards the Overlord's deck size or towards his ability to purchase higher level cards. "

Sitting right there in the Servant section of the CRRG (btw awesome work Sadgit), instead of in the Overlord Cards section where I was looking for it.

Yeah, maybe I should add that to the Overlord card entry, too.