From Guild Wars 2 Wiki
- Mistborn Mote
- Chance at one of the following:
- Extremely rare (see notes for exception)
- Daily limit :
- Every 3 chests guarantees a drop of 3 rare items. There is an effect that plays when this happens.
- After opening 100 chests, you will no longer continue to get the rare items and a different effect will play to demonstrate that you hit the limit.
- If you haven't received a Gift of Aurene by the 1000th chest opened on your account, you will get one guaranteed (one time bonus per account).
- ^ https://www.reddit.com/r/Guildwars2/comments/buqi7y/mistborn_coffers_limitation_in_getting_piece_of/epjaqds/ Alexander Youngblood on reddit