[Faceman]

sequencers are extremely powerful and can be used for several purposes. I use my spell triggers as a fast way to bring down resistances and magic defenses (but Wand of Spellstriking is neice here too if you have ToB)
If you use it often you should pick it if not it's better cast it from scrolls (same effect) after all you have to cast it and then rest to get the other spells you used inside back.
there are three types: Minor SpS, SpS, and SpellTrigger for more info read the manual or go to the site Armen suggested