Imperial Legacy has restrictions on where or how it can drop.
This item can only drop in areas that use the 'Desert' tileset as listed in the acquisition table.
A longstanding bug in the code determining area level restrictions for some divination card drops has been fixed. This means that cards intended to have a high area level requirement (mostly ones that grant item level 100 items) will no longer fluctuate wildly in availability from league to league.
Now has a required area level of 80 according to datamining, confirmed unofficially by GGG dev. [Undocumented This change was not documented by any official sources. It was discovered through player testing or datamining.]