Asset for dynamic world management?

I’m looking into porting software I have from another engine into unity.
One thing that I’d like to be able to have a “Gamemaster” player that can dynamically change the world - for example, to create new monsters, interact with environment, create collectable items and so on.

Rather than reinventing the wheel, I thought I’d ask if anyone is aware of an asset that already exists that does this? I’ve had a look but can’t find anything.

There are assets to edit the environment, such as Multiplatform Runtime Level Editor and uConstruct, but to my knowledge there aren’t any assets that let you define new monsters and items straight out of the box. You could use something like UMA to create new humanoid monsters, but it would require some coding. The same goes for using something like Inventory Pro to create new items.

Thanks for that. The MRLE is a little more hardcore than I was looking for, but is pretty close.
All of my items and monsters will be predefined. I just need a way to dump them into the game “live”. Regarding “interacting with the environment” I really meant the ability to, e.g. right click on a moving platform to stop it from moving, or right clicking on a door to open the door. I realise this would probably need me to program some bits myself, but I was curious as to whether or not there was a framework.