there are two components two this, two spiritual weapon type things

sword of light: This sword does not have any attacks, but when given to a creature, it is given a plus 2 to AC and 10 temp HP. You can move the sword between people with a movement of 20, however if the temp is hurt, the amount left is transferred to the next create that gets the sword, this is the concentration part and will go away if concentration is gone. when upcasted, the temp hp goes up by 5 every level

Sword of darkness: this acts like a spiritual weapon, it does 3d8 necrotic damage with the casters modifier to hit, has a movement of 20ft. if conecntration is gone, this stays, it will stay for one minute and then will go away. damage gains a d8 every 2 lvls