From the Treasury: Mygorum's Portable Librarium

Mygorum the archmage was a rather neurotic and absent-minded wizard. Over the many years of adventuring with The Company of the Blood-Tipped Spear, he accumulated volumes upon volumes of ancient and arcane lore. As the years went by, and his memory began to fade, he found it necessary to have access to his tomes as often, and as readily as possible. Thus, he crafted the device he named Mygorum's Portable Librarium.

The minor artifact is presented as an ornate golden pyramid with bright ruby gems inset along its edges. When placed on the ground, and the proper command word spoken, the mage is transported to an extra-dimensional space within the pyramid statue. Within this space, time stops effectively for 2-12 full turns once per day.

Inside, the librarium is lined with bookshelves along its walls and a small desk and chair at its center. The tomes within contain vast and various spell books, beastiaries, and other such sundries left up to the DM to decide. The mage may make use of this time however he sees fit within the librarium (memorizing spells, researching information on how to destroy a monster, etc.) Once the mage chooses to leave the librarium and return to the prime plane, he returns exactly where he left and time immediately resumes from the point at which he entered the librarium.