What happens to the wreckage created when extreme dead stars clash? 

 Neutron stars are the universe's most extreme stars, composed of matter so dense a teaspoon of it would weigh as much as Mt. Everest. So, when they collide, it's quite the event. 

https://cdn.mos.cms.futurecdn.net/amyhv7rBFvvEsPS5JApj3M.jpg

https://www.space.com/neutron-star-merger-wreckage