There have been rumours of a hidden chest containing a book with a preview for Ultima 9 among other magical equipment. This chest was supposed to be behind a wall beside Xavier's bed, on Argentrock Isle.
Originally, this rumour was addressed by Jeff Abramson's walkthrough and FAQ, which can be found found in many places listed in my Other Walkthroughs section, which dismissed it as a hoax:
1. Where is the U9 preview chest?
Nowhere, the developers claim there is no such thing.
Stefan Gruber pointed out that Jeff Abramson eventually updated his walkthrough/FAQ as follows. This update happened only on his website, and other copies on the internet do not have this updated information. Unfortunately, Jeff's website went down with Geocities, but an archived copy of his walkthrough/FAQ has been found on the Wayback Machine.
"Where is the U9 preview chest?
For over three years, I have been saying nowhere, the developers claim there is no such thing. However pdick@marathon.Lakeheadu.Ca reports that he did find the preview chest (Oct 97), however several other players have not been able to duplicate this. Please try and let me know! On argentrock isle in xavier's house there is a wall beside his bed. Use the cheat and move the wall and there is a chest, in the chest are his focuses, and one for ressurection, a bunch of potions, 2 scrolls, a magic helm and level 2 magic armor, and a book with the preview for u9. He cannot confirm if this is in all versions. One other player cannot find this on the English Patched Version. So I am not yet convinced this chest actually exists."
There are several strong indications that this whole affair was a hoax.
First, Underworld Dragon wrote the following in his Ultima 8 Collectibles page:
Underworld Dragon wrote: And although someone has recently reported seeing an Ultima IX preview chest in the game, I've checked the filestamps on this CD and none are later than mid-1995.
Second, both Kobra Kai and I hackmoved Xavier's whole house to verify whether the rumours were true, but found nothing. Kobra Kai also noted that there exists no level 2 magic armour in the game.
Third, in a 2014 interview at The Ultima Codex, Jason Ely, one of the programmers on the Ultima 8 team, had this to say about the Ultima 9 Preview Chest:
Jason Ely wrote: "To my knowledge there was no Ultima 9 preview chest and if there is one I never knew about it. Nobody knew exactly what the theme of Ultima 9 would be during U8 development. We had some ideas and planned some things later on in the project, though they changed when U9 development began."
Fourth, in 2020, Daedalus hackmoved Xavier's entire house, including the floor, and was unable to find anything. He proceeded to analyse the Usecode files in depth, both pre-patch and post-patch, looking for items such as the level 2 magic armour or the Resurrection focus that would supposedly have been in the chest, and nothing turned up there either.
There is a unique and seemingly useless item - a blue vial that cannot be used - in the Fisherman's Reef area. The vial is located on a bag on a skeleton in a cave behind the waterfall in the north part of the area. It has no in-game label and nothing happens when you double-click it.
The blue vial is also mentioned in the U8 Nitpicks page at The Codex of Editable Wisdom.
In October 2009, Stefan Gruber told me about a special kind of Executioner's Hood, labelled as "sliced executioner's hood", found in the Upper Catacombs. Like the blue vial, this is a unique and (apparently) useless item.
Kobra Kai confirmed its existence and sent a screenshot along with clear instructions about where it is located:
Kobra Kai wrote: It's on a dead body located along the path to the Necromancer who teaches you the spell Withstand Death. There a chest nearby and a fire dart blower (which quite possibly killed the warrior).