I thought you meant 30 seconds. I use commas, sorry, haha... It sounds like a sustained summon.
mmh.. I didn't notice any magicka drain during the summon... Another strange thing is that the death sequence of the summon is not played.... I mean, the summon stays, then it should fall and disappear when the time elapses. It instead disappears without falling.
By the way, I'm reinstalling Oblivion following the TESPositive guide order.
(I always installed Quest Mods AFTER Overhauls.... I didn't know I had to do contrairwise)