The Cycle was upon them.
Their civilization faced oblivion.
They rejected the wyvern’s call.
A stopgap was made - the Lucifer.
Its blade - a laser imbued with the power of many a slayed god - would tear into the apocalyptic beasts emerging from underground, unholy flesh and machinery incinerated with divine fury, with righteous refusal to let the Cycle persist.
When the ashes finally settled, the wyvern and its army was defeated, subdued by the planet it had tortured for countless millennia.

Mekhanos and Pandora Altra are made and owned by Denialiation on BlueSky.
I help design some of Mekhanos’s war machines.

Canonically, this civilization is not only allied with, but indebted to my world setting of O-Realm, as the interdimensional civilization had immediately provided them with Unconditional Material Support upon the observation of traits within Mekhanosian society similar to their own - such as communistic economics and an egalitarian, honor-based culture.