The decking of the bridge erupts in a dazzling display of arcing electricity, with jolts sending the spider's legs into a convulsion that hinders its movement as it staggers forward. But it doesn't hinder the arachnid's aim, as a pair of dagger-sized fangs dive through Huril's mail and deep into his right shoulder.
Spoiler16 damage. DC 18 fort save or (1d4) Str and (1d4) Dex damage
pale blue is Mika's spell (the part not covered by the spider, at least)
Purple = Jon is about 10 feet below bridge deck level. Climbing speed is 1/4 move speed, or 1/2 if you take a +5 DC. You can also move sideways at the same speeds.
Remember, the spider has 15' reach.
Everyone is up