With your combined efforts, it takes only mere seconds to move enough rubble to see that you've partially unearthed an ancient, underground chamber that was buried in the rubble. Within it, you hear a growing humming sound, and see a purple glow coming from underneath the last of the rubble. Unfortunately, all of the digging undermines the crumbling spire that the vrock was perched upon and causes it to fall crashing to the ground.
[spoiler]Everyone within the area of x0, y0 to x-5, y-5 make a DC 20 Reflex save, or take 8d6 bludgeoning damage (save for half).
Concealment within 5 feet, total concealment beyond that, 50 foot radius centered on x0-3 y-3.[/spoiler]
A great cloud of dust rises up in the aftermath, blocking vision over any appreciable distance. In the rumbling and dust, something monstrous breaks from under the ground underneath almost the entire party. It's chitinous bulk seems to be covered in spines, and numerous clawed pinchers swipe and claw at everyone nearby it in a whirling frenzy of rage.
[spoiler]a large beetle-like creature appears centered at x1,y1. It attacks everyone within a 20 foot radius (Xuuvosic, Kaemarah, Erlking, Oggug, Hannavra, Siphsis, and Marlowe): Attack/damage rolls, in that order. If you're hit, make a DC 20 fort save or be dazed.
And Marlowe needs to make an opposed grapple check (DC 16:
1d20+14=16) or be dragged back under the ground with it as it retreats). After this surprise round, I'll roll initiative for it, and we'll keep your guys initiative, if that's OK.
1d20+13;2d4+6 ? [20,13] = (33)
1d20+13;2d4+6 ? [3,1,6] = (10)
1d20+13;2d4+6 ? [4,13] = (17)
1d20+13;2d4+6 ? [2,4,6] = (12)
1d20+13;2d4+6 ? [14,13] = (27)
1d20+13;2d4+6 ? [2,1,6] = (9)
1d20+13;2d4+6 ? [13,13] = (26)
1d20+13;2d4+6 ? [2,4,6] = (12)
1d20+13;2d4+6 ? [5,13] = (18)
1d20+13;2d4+6 ? [4,2,6] = (12)
1d20+13;2d4+6 ? [20,13] = (33)
1d20+13;2d4+6 ? [2,4,6] = (12)
1d20+13;2d4+6 ? [11,13] = (24)
1d20+13;2d4+6 ? [3,2,6] = (11)
[/spoiler]