The invasion of the multiverse used omenpaths to traverse their troops. These omenpaths reached prison inside Ugin's meditation realm. This allowed Nicol Bolas to escape and influence Ashiok to help him create a virus that would infect beings and make planeswalkers sparks unstable. With this planeswalkers all around the multiverse start sparking and desparking in chaos. And the Virus is spreading. One by one it infects animals and other creatures. The multiverse is for sure doomed.