This is an event Craft Essence. It can only be obtained by participating in a time-limited event. This Craft Essence cannot be summoned.
Event reward and rare boss drop from the Christmas 2015 Event. During Santa Alter for About a Week, Holy Night Sign increased the chance of getting an additional Magic Sock drop by 20%. The additional Magic Sock drop could have a different base count from the original drop. This effect was additive, stacked with the Servant bonus, and counted if your support Servant was equipped with it.