A couple of Ricks saw the impending doom that would befall their dimensions. They gathered together in order to avoid this travesty. The plan was to merge their dimensions into a single new dimension in order to escape calamity. They knew the risks and odds were not in their favor but they had to try.

Their respective Mortys were against this plan as it meant losing their home and Rick. Rick had to stay as the conduit to preform the merger but since Morty was so concerned, they were sent to the Citadel of Ricks. . to safety. 

The merge of the dimensions was successful and avoided the disaster but the world was left with a permanent scar as all the inhabitants were fused with alternate versions of themselves and now shared the same body.