Tiger Heart Chest
This chest was crafted especially for the Heart of the Tiger Festival, using materials from both celebrations. It looks like it requires a key from each holiday to open.
Tiger Heart Chest was dropped by the Red Envelope Mouse in the Heart of the Tiger Party. It needed two keys to open, the Heart Key which was dropped by the Cupid Mouse and the Tiger Key which was dropped by the Tiger Mouse. From 22 February all three items were able to be exchanged for contained 30 pieces of SUPER|brie+ and a Dev Love Note, which appears in the Gifts Tab of the inventory as Valentine from the Devs. (The link for this exchange was found here.)