Not sure how but while running through the overworld wilderness I ended up in a dungeon getting shot by about 20 archers at once that killed me in a few seconds, how I got there, did the wilderness eat me or something?

theres some cracks in the ground that you can click to go down into some maze with a bunch of shit that wants to kill you

You entered a part of the chaos tunnels. Every monster in there is aggresive which means it will always come and attack you, and since it is a multi combat zone, more than one will come at you.