I'm just getting into the Terrinoth mythos, and it's captivating! One card that I (and my boys) really love is the Everliving Engine from the Monuments scenario. Here's the text:

No one knows what the machine does, nor what makes it run, except that its churning somehow aids the Undying One. Its bony wheels grind in the volcanic caves beneath the ruins of Kelipa, where it is maintained by the Archlich Revik. Kelipa is only a few short miles from the edge of the mists.

On particularly quiet nights, when the wind blows in the right direction, the clacking of the Everliving Engine can be heard for miles. The farmers and woodsmen brave enough to live nearby do not sleep easily on those nights…

It gives me chills! Love it! But it got me thinking: what might the Everliving Engine be used for? I don't really want them to reveal it - it's much cooler for it to remain shrouded in mystery. But what are the rumors whispered between the villagers close to the mists? What wild ideas have risen in the minds of villagers, soldiers, and adventurers who have heard its eerie echoes?

My supposition:

Waiqar and his original forces died and were reanimated in that fateful night when Waiqar attempted to steal the Sky Orb from Timorran Lokander. His wretched oath upon a shard of the shattered orb drew enough power to give him an army of living dead. But what of the other forces that serve with him? Did Barrow Wyrms and Wraiths and Barghests join him on that night? I doubt it. My guess is that the Everliving Engine generates the dark magic used to reanimate new forces and to maintain those that were brought back from the dead.

If that were true, though, it would be a huge target for the Daqan forces to overtake.

They actually answer this in the Realms of Terrinoth book. It's ripping a hole in the veil between the world of the dead and the living. "Waiqar’s most heinous vehicle of destruction,
the Everliving Engine, is a machine most
foul. Deep below the volcanic caves under the ruins
of Kelipa, its bone gears grind endlessly with
a sound that reverberates across the Mistlands. So
great is its mechanical noise that, on still nights,
the sound can be heard dozens of leagues away,
as far as the border of the Barony of Carthridge.
Its true purpose is known only to Waiqar and the
archlich Revik, who oversees its operation, but with
every tick, the barrier between the world of the living
and the dead weakens. The undead everywhere
feel themselves empowered, if only by the faintest
margin, and new, unimagined horrors manifest to
plague the world of the living.
Those who displease Waiqar are fed to this terrible
machine, and their screams mingle with each tick
until they are subsumed entirely. No mortal can
say exactly what it means to be consumed by the
Everliving Engine, but it is a fate dire enough to
strike fear into the hearts of those who serve the
Undying One."