I have been using two of the symbols of bane from E. A. Koetting´s Baneful magick. Although they have weakened my enemy, they work too slow, so I want to use them both at the same time; well, on separate days at least.
EA says it is good to use several ways simultaneously for your dark goal, but then it also known that one reason for a spell to backfire is using several demons simultaneously - they can get offended and give you a good spanking. However, one of the sigils is the last one - a talisman calling all the Infernal hosts, so that in itself is several demons. I am ambivalent here.
When it comes to death magick it is not a time you want to risk your spell backfiring, so I thought I would ask for a second opinion.