CommentStreams:77c6c1aa23ea47bc575e426332beea5e

The reply above is too vague. The skull key can only spawn as loose loot in the bottom middle module on Inferno Map #1. Note that currently there are only 2 Inferno variations at this time. Map 1 has the module (Module is listed as Demon Throne). In Map 2 this module is not the same and is instead the location where you can use the skull key (Module is listed as Demon Gate). Hope this helps.