More wacky-looking ethereal monsters!
The chassis is quite attractive, with two magical beast RHD. Stat boosts are less great, but still positive overall (+4 strength, +2 dexterity, +2 wisdom, -4 intelligence). Speed is above average, and NA is not bad.
The bite attack is weak, but that matters little: any self-respecting meleeer would be using a Mouthpick weapon already. Finally, there's the skill bonuses: Spot and Listen are always useful, but Move Silently is useless for a certain reason.
That reason? Ethereal Jaunt. Marauders can shift to the material as a free action, then back to the ethereal as a move action. Amongst other things, this guarantees a surprise round that places you next to an opponent, near-perfect scouting, great puzzle-solving and awesome in-combat defenses.
So what LA to give? If it weren't for Ethereal Jaunt this would be an easy -0, but with it the situation changes. +2 seems best right now, but all alternate perspectives are welcome.