Ye Olde Inn

Sirs.
I play the role of Zargon and when I finish a book, I have a doubt about the expansions, do the heroes keep their items and artifacts or does the system return to its original status?

An example. They finished the expansion the return of witch lord, and the elf had a crossbow a shield and a helmet, in the next expansion he starts with the items?

Yes they keep all items as they proceed. That’s why the quest packs get harder as you advance to balance.

Correct. In a few rare situations the quest tells you that an Artifact or Special Treasure has to be returned or whatever at the end of the pack, but usually you can keep it forever. Technically if an Artifact is ever "lost" (claimed by monsters when the one who kept it dies) Zargon is supposed to make it available again to find as a special treasure early in the next quest (unless the text says otherwise of course).

The EU original didn't allow Heroes to keep things found from the Treasure Deck (other than gold and gems/jewels which are cashed in for gold) from one Quest to another, while the NA edition (upon which the Remake is based) allows you to keep them until they are used up (you don't hang onto the cards, you write it down on your character sheet, and the card is re-shuffled into the deck on the NEXT adventure).

Technically if an Artifact is ever "lost" (claimed by monsters when the one who kept it dies) Zargon is supposed to make it available again to find as a special treasure early in the next quest (unless the text says otherwise of course).

I hear this rule quoted often but I think this actually only refers to artifacts that are lost AND are needed to proceed further in the journey, for example if you lost the Spirit Blade at some point in the "Quest for the Spirit Blade" then the GM would have to place it somewhere towards the beginning of the next Quest "The Return to Barak Tor" otherwise it wouldn't be in play to fight the Witch Lord which is the point of the artefact as it is the only weapon that can harm him. if for example you were to somehow lose the Elixir of Life then there is no hard and fast rule that the GM needs to place it early in the next Quest, although it would be appreciated if he did!

Very few Artifacts are truly "Needed" in the way the Spirit Blade is (even that one, if lost, has a second chance to find it again... or rather if it was never found to begin with, in ROTWL).

The text kind of says both. Sometimes Artifacts are required, here's a way to find them again. But it gives a universal statement. I guess Zargon can interpret it any way he wants to...

Presumably this rule was made to avoid the obvious other alternative (replay the quest to get it again, rinse, repeat). The 1991 pc game for example forces you to do this (with no changes to the quest, pretty dull).