For those of you who don't know, this feat is the psicrystal's version of improved familiar. Basically instead of a psicrystal you get an elemental steward (Complete Psionics p.130) and the elemental steward gives you all the benefits your psicrystal gives.

So why is this feat AWESOME? Because of GEODITES.
1. This feat is obtainable at level 1.
2. Geodites have DR5/- AC17 making them absolutely phenomenal tanks at low levels.
3. Geodites have BURROW SPEED that can BURROW THROUGH STONE. This is why Elemental Envoy is fantastic! It's basically an at-will non-combat disintegrate. You can destroy walls, bypass vast portions of a dungeon (like a trap or a gate that cannot be opened unless you solve a puzzle) or create choke points (by forcing enemies to fight in these small-sized tunnels and which forces them to squeeze) and force the enemies to fight on your terms rather than theirs. You can create a rest area in the dungeon and cut off all entrances by causing a cave-in that can be re-burrowed through.

The reason I'm posting this is because the guides I found online all say this feat is terrible and it's not true. Geodite's combat capability may becomes nonexistant after like level 4 or 5 but the burrow speed should stay relevant for a really, really long time and at level 1 they're a contender for most powerful minion.

During my play test at level 1 the Geodite solo'd entire encounters due to his DR5/- and at later levels I used the burrow speed to attack and retreat like guerillas and when the enemies gave chase into the tunnels the Geodite would block their path with a Tower Shield while I killed everything with matter agitation. For stronger encounters I got creative and spent some time setting up traps in the tunnels that would completely block passage when triggered to secure a retreat. That way I can matter agitation a creature, retreat, and then just sit there concentration for a minute or two to kill the guy who can't stop his death because a giant rock is blocking his path to me.