Preceding this is general history of the Elder Scrolls world and some small summaries on the stories of Arena and Daggerfall; if your read up on your lore your not missing out on anything.
''"Battlespire takes place during the time of Arena (roughly 3E 399) in a majestic tower, if you will, a medieval space needle, inhabiting its own pocket universe. Originally a war college for the training and sharpening of imperial battlemage skills, evil forces invaded this citadel of military of imperial battlemage skills, evil forces invaded this citadel of military civility. Now, monstrous minions block and thwart your every move. You must escape back the benevolent confines of Tamriel at all costs.
''During this time, a host of societal institutions were suspended in so-called "pocket universe," to achieve a state of immaculate virtual reality. One such institution, deep in the ethereal place of Aetherius is the Battlepire. It is a proving ground, or sophisticated war college for prospective battlemages. Five special anchors clamp the Battlespire in place, connected immediately on arrival when towed in by the Great Star Galley. If all anchors are disconnected, the Battlespire drifts outside of the nexus of rich magicka-currents, the entire platform goes black and dead, and the PC, the Battlespire, and everyone there perishes.