@merlin
The vomiting spiders sound weird and creepy, essentially are they crawling up your throat or just appearing in your mouth?
To where it's cool, but would try not to vomit..vomiting... may be added challenge when tempted and feel living spiders in your mouth trying to escape.
For a swarm of biting flies would be interesting to summon, but would you just be summoning them to eat yourself? Especially if they are biting flies surrounding you.
I dislike crawly things, but morbid curiosity makes me choose the spider vomit, hopefully it's useful or I never vomit.
Question: would you rather be a portal hopper and need to change your world every week, or live as an immortal being (elves or vampires)?