I wouldn't use the term 'engineered', given the trial and error involved. About 10000 years ago, Igeyorhm tried to brute force a rejoining on the Thirteenth by attacking and killing its heroes. Not only did she successfully eradicate life on the Thirteenth, she also rendered it uninhabitable, turned its denizens into Voidsent, and made a rejoining impossible. The Ascians learnt from that mistake, but each subsequent rejoining involves the destruction of all life on the reflection in question and a massive catastrophe on the Source. By the time our journey started, they had killed off eight worlds including the Void, and rendered one mostly uninhabitable, with the intention of using chemical warfare on the Source to expedite the associated rejoining. Their ultimate goal was to kill off all sundered life across the fourteen worlds so that they could perform more soul microtransactions with Lord Zodiark to rebuild Amaurot again.

It was a pretty bad plan from the outset.