A magical box, small and ornately detailed on the outside, a vast and infinite void on the inside. Created as a prison to hold elementals, the box changes forms depending on who is trapped inside of it (ie; turned icy colored with Lucifer Deitus inside). One hour outside of the box is the equivalent of one hundred years inside, and the person imprisoned inside nearly always goes mad.
The Box of Ensi can only hold one entity.
Lilith is perhaps the most famous (or infamous) victim of the box. She was imprisoned within for over 2,000 years, which totals to over 2 million years in box time. She is the most extreme case of the box's solitary realm driving someone mad, with Lilith's own insanity actually taking physical form, and birthing her powers of darkness.
Lucifer, with his final defeat at the hands of Vries, was imprisoned within the box. The box was then buried, with every intention to leave the Ice Elemental trapped for eternity. After a year, with the arrival of The Sun Tribe on Haven land, the box was found by Nila, and Lucifer was set free. It is debated whether or not the box made him a friendlier person or no change whatsoever, seeing as how Lucifer was already quite insane before his imprisonment.
Vries was momentarily trapped within the Box of Ensi during his final confrontation with Lucifer. After finally defeating his nemesis, Vries escaped.
The Firstborn of Fire was actualy briefly imprisoned within the box. He was decieved by Lilith, and did battle with her within before managing to escape shortly after.