Far as I know (and I don’t play in SR so I could be wrong) you can get a blueprint for a Waystone at levels 5, 20, 35, 50 and 65 which you can then learn and make the stones at a blacksmith to use. They’re a way of saving you from having to run from 1 to 5 again to reach 5 for example; instead talking to Mazaan gives you the option to use a Waystone to start at whichever level a particular stone unlocks. I think you still need to make your way to a particular shard before you can access it, i.e you can’t use a Shattered Waystone when you reach 5, exit and then give Mazaan the stone to access 15 - you need to reach 15 first, but can then start a new SR session at that level once you’ve unlocked it.
If you continue to plow on from 75 into the higher Shards then I think loot does still drop. But if you use a Death’s Waystone to reach them then it’s no loot, just glory.