Greetings fellow Dungeon Masters!

What if you could Frankenstein creatures together while they're dead and revivify them back with all the new parts?

Mending allows you to "repair a single break or tear in an object you touch." How general is this? Could you mend together two halves of two different keys? Or two halves of two different lengths of chain?

Could this allow you to mend one mans arm onto another mans shoulder and create some crazy Necromantic monstrosity?

I don't think repair means what you think it means. I would only allow mend to fix things - as in undo breakages or damage.

Reattaching an arm is not a single tear.

there are tears in muscles. Tears in ligaments. Tears in skin. Etc.

now. If the person who died, was a hemophiliac, and had a single scratch that tore through their skin. Yeah it could work then.

When I think of mending I think of restoring a thing to its earlier unbroken condition, not grafting parts of different things together.  Mend is simply a cantrip, after all.

But if your DM likes it then you're in business.

If you are the DM and want something like this, then I would homebrew a spell of the appropriate level.

My 12 year old sorcerer tried to “mend” a friend who had been stabbed in combat. I knew as a player it would not work, but my character had no idea whether it would work or not so it was worth a try. I did however mend my friends leather armour in the attempt.  

 RAW, definitely no.

As a DM, I'd probably allow a combination of Revivify + Mending to bring a creature back to life with missing limbs reattached (or potentially frankenstein-replaced) because it would be cool.

You could reattach to halves of a key. Or, two parts of a broken chain if you have both of the broken parts of the link.

Revivifying monsters dr. frankenstein syle? No. 

No.

A creature weather dead or not is not an object.

If that creature was turned to stone and then broken...maybe

Dead creatures are technically objects, iirc.

In this game? Really?

Morbid ass game dev's. Tell that to the family of the dead IRL. 

Just checked...dammit J Craw! No boundries.

There's a few issues with this that others have stated but one of the biggest in my opinion is that spell specifically states it's parts of the same item. So mending any parts that were not of a whole before wouldn't work.

So, yes, corpses are objects. 

You can't bring people back to life this way, but you sure can reattach a dead arm to a dead body, if you have enough time to do that. 

You cannot reattach a dead arm to a living body. You'd have to kill the person, mend the arm back on, and then raise dead on them. 

Mending a dead arm from a human to the dead body of an orc doesn't work. 

Yea, they are objects but attaching someone's arm to another persons body, object or not wouldn't work because they were never part of a whole. But I agree, if you have the time to put the same persons arm back on his body that could work. I'd think it would take a while having to go layer by layer from the bone out.

Yeah. Is a bone considered a different object from skin, or muscle? I'd have it take 3-4 mendings to reattach it. 

This is what I was thinking. There are probably a ton of other meaty bits inside the body that would need to be healed afterwards but as long as you get the major blood vessels, bones, and muscles it would be a functioning arm right?

Yes, because Mending restores hit points to the object. (NOTE: to the object, not the creature. Mending doesn't restore hit points to the person that died, merely their corpse.)