When they're bringing Elektra back, the Hand mix a dark powder into the blood and they dump all of that into the container with Elektra. I'm assuming the dark powder is the dragon bones? But the showrunner said that Gao was using the bones in her heroin which is why it was so strong. I like knowing that but I wish they'd showed it. Someone said it was inferred at some point by the Hand but I missed it on the show.