Thanks for the latest ideas:

Sounds right to me so far. I'll toss in my Single Leg trait too, as a 0-point option that adds a little extra detail. http://www.gamesdiner.com/gurps/GULLIVER/B3body.htm#NumberLegs

I agree that we gotta make some assumptions, even if only based on little sketches. (And hey, it's appropriate: Sathar are rarely encountered – and never caught – alive; everything about them should be guesswork. : ) As you and the sketches depict it, the lower tentacles are essentially arms, stronger than the upper arms but with poor manipulation. I think we're agreed there. My question is: does 4e cover building mismatched sets of limbs (as in two types of arms)?

As for the limbs' utility in "standing", I think no extra complication is needed. Even if the limbs were just plain arms, they could be used for this purpose, as a special effect of where they're positioned. Just as limbs positioned high on the body would be particularly useful for reaching high places, no special trait needed. (And that's where the Sathar lower limbs fall short.) They're arms that happen to be well-positioned for placing on the ground.

However, that "tripod effect" should make for a much more stably-standing worm, worth some bonus on balance checks. I'll have to dip again into GULLIVER for this optional extra detail, unless 4e offers something other than Perfect Balance (which would be overkill).

The final question, if I'm not missing something, is whether the lower "arms" are needed in some way for normal movement. If yes, then that's another complex point adjustment. Perhaps it's just easier to say they're not needed for movement and do nothing to aid it, other than to improve balance (already covered above). Or to drag the Sathar along if his regular movement appendage ("tail") is injured, but as any default arms can be used for crawling like that, no special trait is needed for that. What do you think?

I'd like to make it some subset of Charisma, "Only for Intimidation or similar forceful interactions, not for friendly interactions". But I don't know that 4e handles that.

How about a Talent for Intimidation, Leadership, Enthrallment (with the Talent substituting for the Charisma requirement), and Hypnotism?

I like Sathar too. The "fifth column, voice-in-the-dark, puppet master" aspect is what makes them cool. Any enemy worth its salt has to have some weapon far more subtle, and open-ended in damage potential, than combat prowess; it's pretty much a requirement for an arch-enemy race. Without it, an enemy becomes Orcs: fun, yes, but generic combat fodder, just the foot solders of the real enemy with the subtle/sophisticated power.

Even Fantasy Folk's Verm get Sathar-like treatment: wicked psi powers on top of the armored combat crab shtick. They'd be one-note foes without it. The psi aspect opens up whole new possibilities.

But, subtle psychological warfare aside, my best-remembered Sathar game was an old-fashioned cat-and-mouse-and-blow'-em-up conflict between PCs and Sathar (and some robots on each side) on a large space ship map. Lots of corridor chases and firefights. Which, if you count the explosive weapons as fireballs, pretty much translates to "dungeon". ; )