The yogpstop mod spawner thing crahed the server when you right click on the item after it is placed down
It contains a few random items but the item he is talking about needs to be banned in my opinion as you can change a spawner to any spawnable item in the game including things like the ender dragon and even entity's can be spawned from it
go to 29:50 and you will see the block and all the things it can be change spawners too just to show you more info
