Special Note on Magic Items Encountered During Adventuring
A magic item you or another member of your group had access to during adventuring becomes linked to your character’s progress. If a player has multiple characters, only the one that joined the group that encountered the item becomes linked1.
Even if you have not retained the item during the adventure, and even after you switched the item at the armory for another one, you may still exchange any of your magic items for that item at the armory1.
Though you will have the item as an option in your personal armory, only one character can retain an item you encountered beyond the session1.
For example, you joined a group where the fighter earned a Flame Tongue Longsword, a rare magic item. The fighter will retain the weapon and can keep it as long as they have an open slot for their magic items. They will also add the Flame Tongue to their armory, as will all other party members in that session. Everyone who joined that group can now change any of their rare or higher magic items they have in their inventory for a Flame Tongue Longsword. You cannot trade a lower rarity item up for a higher rarity, even if you switched one down before. Only tier 4 characters may retain Legendary items.
You may not trade magic items you encounter during adventuring with characters that did not join that quest.