I'd like to use this badboy at the next session, and I was wondering if anyone has any suggestions of things to consider for stats?

Thanks in advance.

Need a sense of scale: is it coming out of an apple? A cave floor? An asteroid?

My first thought is to have them fight this guy alone (assuming its pretty big and beefy) and have it burrow underground at the end of its turn once or twice. While its underground, allow the PCs to get creative: take a breather, rolling a skill to predict where it will appear on its turn, or anything else they can imagine. A turn where attacking just isn't an option has the potential to inspire some out-of-the-box thinking.

The burrow idea is fun, but you'll need to have a solid ruling on how you deal with "readied" actions. They're not supported by RAW, but some groups have house rules for them.

Its about the size of a purple worm from D&D. I didn't end up using it as my PCs came up with a much better idea which meant I didn't need to use it. I'll save that for another time. Oh, and I decided it was going to be burrowing in an out of asteroids.