The base loot system was replaced with the loot revamp we did in Pub 86. The RNG was replaced with a more modern version (Bleak made a post about it some time ago). Luck (the stat) only works when we are actually pulling that value into some calculation to determine the outcome of an event. We use the luck stat a couple of different ways depending on which system we are dealing with, across a variety of systems. Let's say for example we want to determine whether or not you get a "rare" reward. In order to do so let's say you need to roll >99 when we pull a random number between 1 and 100. Let's say you roll a 2. In this case we may pull luck in and say, if your luck is X, and a random number between Z and Y is greater than X, you get another chance to roll for the rare. In other situations we may take a portion of your luck and add it to your roll to see if you win the rare. It varies system to system, and it only does exactly what we tell it to. Nothing more, nothing less. In the case of loot item property generation, there is more complexity that goes into determining what properties get applied. Look for more detailed information about this process in our newsletter, which you can sign up for on UO.com.