It just makes it so you can loot your corpse a little more easily, and have a few extra inventory slots, because it provides a special extra keys-only bag (essentially).
It's one of those things that pretty much undeniably made the game better, but it truly wasn't there in classic (ie. the whole point of this place). Then again, neither were custom UIs or pet windows, and keyrings came out at the same time or very shortly thereafter, so they're "grey" enough (classicly speaking) to start fights here
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