darkstone sword

you start chanting a dark chant, and slam the darkness crystal into the sword, creating a darkstone sword. It's power is great, and it is very deadly. it is far more strong than stone, and is only breakable by the means of magic. it acts as a Shortsword that you are proficient with but deals 2d10+your spellcasting bonus in slashing damage, and an extra 3d6+6 necrotic damage. you have an attack bonus to it equal to your spellcasting bonus + your charisma bonus. you can throw the sword and make a ranged attack against a creature, dealing half the damage you would normally do. it then will fly back to your hand. it can only be used by the spellcaster. anyone else who tries to wield it will have to make a DC 20 charisma save, or take 3d10 + 15 necrotic damage.

after a week, the sword reverts to it's normal form. the crystal looses it's magic and shatters.

when cast with an 9th level spell slot, the duration increases to 3 weeks, unless casted by 3 or more people at the same time. then, they create 1 darkstone sword, with o duration. it will last forever. a darkstone sword created this way can only be destroyed by a wish spell.