This came up in a discussion with a fellow 5e DM:
A player casts Animate Object on 10 daggers. This makes 10 animated daggers with 20 HP and 18 AC according to the 5e PHB. Now according to the spell "When the animated object drops to 0 hit points, it reverts to its original object form, and any remaining damage carries over to its original object form." This is all fine and good.
The 5e MM says something similar regarding animated objects: "An animated object reduced to 0 hit points becomes inanimate and is too damaged to be of much use or value to anyone." Everything seems to agree.
Now, the DMG lists tables destructible objects. Daggers we presumed to be Tiny objects which according to the DMG would have 2 HP if fragile, and 5 HP if resilient. Under Object Armor Class it lists Iron/Steel with a 19 AC.
Here's where the argument comes in:
According to the PHB, Animate Object changes the form of the object to a construct creature with 20 HP and 18 AC for Tiny objects. When it reaches 0 HP it reverts back to its original form (We're assuming an object with 5 HP and 19 AC), with any excess damage carrying over to that original form.
So what happens when the daggers reach 0 HP taking into account the PHB, DMG, and MM?
Argument 1: When the animated dagger reaches 0 HP, it reverts back to a regular dagger with 5 HP (a la Wild Shape Druid feature), suggesting that it needs to take at least 25 damage to become unusable. The animated creature construct form is separate from the inanimate original form, therefore damage applied to the object in animated form is separate from damage applied to the object as a whole.
Argument 2: When the animated dagger reaches 0 HP, it becomes inanimate and is too damaged to be used, suggesting that it only needs 20 damage to become unusable (a la Shapechanger NPC feature). The animated creature construct form and the inanimate original form are still the same entity, therefore damage applied to the object in one form applies to the object as a whole rather than just to its animated nature.
So when or how do the daggers become so damaged that they're unusable?
I've seen this answered for 3.5e and Pathfinder, but not for 5e and after hours of trying, unsuccessfully, to find a 5e answer, any insight in this would be appreciated :)