re: Question for anybody that watches the Originals.

Ok basically the black dude witch came back with the sole purpose of channeling a bunch of dead witch's powers into that bone dagger. It can't kill an original but immobilizes them, similar to the daggers, but it also causes them extremely severe pain the entire time they are immobilized. Klaus was stabbed with it and tortured.

While he was being tortured the hot red head witch showed him how she helped Rebecca and Marcell locate Michael and bring him to Nola bc they wanted to be together and Klaus wouldn't let them. It's actually a pretty cool episode that shows the events of the originals time in new Orleans in the early 1900s. But that's why Klaus is trying to kill Rebecca in that graveyard.