*SPOILER* So I think the new primal in 3.5 part 2 is...

[Belhi]

Just to make a point about the "legs" in the Cocoon: those are just the swords on the other side of the translucent shell as it forms. It you compare the hilts of the swords, they all have that sort of wavy characteristic that may look like legs from a distance, but they're just silhouettes of the swords.

These don't look much like the sealing spear things to me. They look like legs.

[Darkstride]

These don't look much like the sealing spear things to me. They look like legs.

Look at the shape of the Spear Heads:


Then see the angles where the 2 bottom spears penetrate the "cocoon". You can see that certain angles, as well as spearheads inside the sphere, appear as shadows:


You can then see that where the spears penetrate the sphere, the portion inside appears dark as a shadow and at that particular angle, the shafts fade into the back: