Ratty Stinker 3000

This works as an enchanted long sword 1D8+2.
The works as a thrown weapon. On a successful
hit, the target must make a CON save (DC13) or
take 3D4 poison damage. The sword then spawns
1D20 rats then spawn (acting as a swarm and
doing acid damage). After 5 rounds, each
surviving rat explodes in a 15 foot sphere centred
on the target for 1D6 fire damage per rat.
I'm a rat. I'm a rat. I'm a very clever rat.