The Backpack

The enemy has an Anima Engine. The good guys have The Backpack.
A cursed Bag of Holding III, The Bag of Containing opens up to a pseudo-extra-dimensional space in a 9ft cube. The orientation of the bag when opened relates to where it links up with the space. The bag itself looks like it is made of simple leather, although it detects as magical, and careful inspection reveals shoddy runes sewn into the pack with silver thread.
The space inside the bag is invariably a chilly 10 degrees, dark and airless. Filling the bag with gas works to some extent, but air seems to leak out over time. Nothing can be thrown through the opening, it has to be manually pushed through. Time passes inside the bag at a standard rate.
The space inside is not true extra dimensional space; it simply folds normal space up tightly. Thus, creatures and mass inside the bag count against limits for teleport-like spells. The advantage of this is that no one can teleport into or out of the bag, making it a safe place to store prisoners and protects from surprise attacks.