jeredu:

The circumstances surrounding Jade’s artificial heart in [ Destiny Star ] are a source of stress for Peony. Rather, Jade’s potentially guilt-driven attitude of having little regard for his own safety when others are in harm’s way (stemming from a childhood incident involving their beloved teacher) has led to close call after close call. This time, Jade doesn’t escape unscathed. 

An incident during diplomatic talks between Malkuth and a neighboring system goes sideways because of sabotage, and Jade ends up staying behind to steer a burning, crumbling ship into the foothills of a nearby mountain instead of the densely populated city it was headed for. Everyone else has safely evacuated, Peony included, but when Peony realizes that Jade is still on the ship, he has Aslan Frings turn the escape vessel around (as best as he is able) to tail the ship.  Emergency responders are already en route, and Peony arrives just in time to see them pull Jade from the wreckage. 

Jade has a chest full of shrapnel and actually goes into cardiac arrest.  He wakes up with a rudimentary, artificial heart. His condition was too serious to relocate to Malkuth proper or wait for state-of-the-art cybernetics to be brought in. While he could upgrade it, such a procedure could kill him, so he chose to live with the primitive design.  

Peony finally has a solid heart-to-heart with Jade about his disregard for himself and the people who care about him, and it finally seems to get through.  The Jade of the present is far less reckless.