basically, to do this, you would make a item/weapon (the skull) and run around with it. and its ability is to slam people with it.
then, in the code, you would basically make a timer in the script that activates when held. and call a function for when its dropped, that the timer would stop, and "messageAll" the time it was held and who was holding it.
It would drop by detecting the players death, and placing it on the ground, like the Ball pack thats default to wait until someone would pick it up. then the in the code, you need to tell it to start the timer, and restart the process.