the ability to create instances in otherwise non-instanced bosses.
cheaper item retrieval services (maybe free at elite)
noted drops from bosses/monsters in areas you've already completed the elite diary for (like noted drops from obor if you have the elite varrock diary)
greater drop chance for the giant keys and ecumenical keys
a restoration pool near a teleport (like the one in the ferox enclave)
the ability to challenge slayer bosses without a slayer task a number of times per day
the ability to send your butler to retrieve items from an item retrieval service for you?
the ability to make "taunt tablets" that work like normal tele tablets except they reset your aggro timer.
the ability to make "peace tablets" that work like normal tele tablets except they make monsters unaggressive towards you for a duration
the ability to "upgrade" dragonstone jewellery to function as rechargeable versions of other telepo...