i just got this add on recently. it only cost a dollar.

the strongest one i had so far was drain health 200 for 3 seconds. not bad since i had drestruction magic at the time.

Yeah, any time you get one that has a stronger effect than you can create at the spellmaking altar it's pretty handy. I like it when I get Baltham's Insight early on - Detect Life 150 ft for 5 secs. The short duration means you have to cast it pretty often, but the 150ft range is exceptional. Very handy for knowing when you need to sneak or not in a dungeon crawl.

You are describing Touch of Death - 250 points of Drain Health for 3 seconds. Very powerful spell, will polish off many foes with a single cast.