The cubile animus is Latin for "Nest of Souls"
Jesse, also known as Reverend Horace Black, wanted to find the box so he could use it to revive the Black Army, his evil 219 followers that were burned alive at a stake. He planned to do this by taking the souls from the 219 Duskers at the advance screening of Dusk III: Unbitten and transfer them into the box to recreate the Vampire Army. Ethan, Benny, and Sarah stopped him by opening the box with the souls inside and letting the vengeful souls fly straight through Jesse's heart, killing Jesse