They were depicted as a shadowy Faustian organisation who acted as the main villains in a range of initially successful but short-lived comics launched in the US by Marvel UK in the 1990s.
[1] The board of Mys-Tech, a multinational corporation, were originally seven mages who in 987 sold their souls to the demon Mephisto in exchange for immortality.
These headquarters were used to house the arcane magical technologies the board used to increase their power and keep the supply of souls flowing to Mephisto.
In the mini-series Mys-Tech Wars (1993), by Dan Abnett and Bryan Hitch, their forces fought most of the Marvel Universe's assembled heroes.
In the resulting demonic invasion, many of Earth's heroes (including a majority of the Avengers, Fantastic Four, X-Men, Spider-Man, Ghost Rider, and Nick Fury) were slaughtered.
The country's heroes fought them back at the Battle of London Bridge (later covered up) and took the Museum of Pagan Antiquities, sending the board to Hell instead and leaving the group seemingly gone for good.