The Teleport spell seems to have a bug. When you roll a mishap, you take 1d10 damage then reroll again with 1d20+80. Which, in nearly every case guarantees that you roll a mishap again. Basically, if you roll a mishap on anything other than a location that you've studied carefully, you take infinite amounts of 1d10.
If the intention is that you die, it might as well say that. I suspect that they only wanted it to do a bit of damage and then teleport you to a similar location instead of where you wanted to go. But someone changed the chart for that the mishap chance was larger.