I realised recently that the Thran Empire, in Magic the Gathering card game, has quite a lot of similarities to Blackmoor: it is an ancient empire that made wide use of technomagic (or something fairly similar to that) and fell long time ago due to some obscure curse (connection with the Pyrexian plane of existence). It was covered under the icecap and Argivian archaeologists unearthed some strange artefacts and they are studying them, but the artefacts are often unstable and can cause nasty side effects, but they are also powerful items that can turn the tide of a war.

Magic the Gathering isn't famous for having interesting setting descriptions (maybe recently they did that as well, I don't know, as I used to play this game during the past millennium) but for the flavour text on various cards and for the descriptions of monsters / artefacts / spells. I do believe that, under this point of view, there is plenty of stuff that can be raided (stolen with pride).

This is the MTG Wiki article dedicated to the Thran Empire (I do believe that there are many more in-game references than the few reported, maybe it is just a matter of searching the right terms): https://mtg.fandom.com/wiki/Thran_Empire
This is the MTG Wiki article for the "machine hell" plan of Pyrexia, that was ultimately the cause of the fall of the Thran Empire: https://mtg.fandom.com/wiki/Phyrexia
This is the MTG Wiki article for Argive (that can be somehow associated, in our point of view, with what Mystara is for Blackmoor: https://mtg.fandom.com/wiki/Argive

I do think that there is quite a lot of cool stuff just waiting to be dug out.

Cool,
I know very little about MtG :)

-Havard

There is a mine of cool flavour stuff that can be easily stolen with pride.