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.
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