In human form is the only use for this other than that when not in weapon form you're just a basic human, also you require an emotionally attachment with someone in order to become there weapon ex: gets their live saved by them.

like a human you get to learn one extra languange

Turn into a weapon when emotionally attached to someone. must have had something specefic happen between you and another in order for this to happen.

When you as a weapon gets destroyed you automatically are put into a death save state if just broken in half as a weapon or something you just roll a d20 to see how much damage you take and are automatically turned back to human form. also if you're user dies you revert to human form.

Every 20 souls eaten is a increase in damage for the weapon roll a flat 1d8 for example my weapon does 1d6 +2 I roll 1d8 and get 3 it now does 1d9 +2. every 100 you become increasingly rare every 50 you can change the weapon you are, you must keep track of your souls. also make your weapon form in homebrew start at common and must have basic weapon stats since you are basically just any other weapon to start.

When in weapon form you dont get to move or attack you are controlled by the person you have emotional attachment with.

when in weapon form your user adds half his modifier unless its a one for STR/DTX/CST ETC, and yours so if he has +1 strength you have 3 he goes 1d6 +4