What sort of things might be immune to petrification?

[CoI]

My players are about to go into an area that slowly petrifies everything inside it. What sort of monsters and encounters would you suggest? The area drains all energy from things until it turns to stone. I know cockatrice are immune, as are basilisks, but I'm having troubles finding other things that might live in an area like that, that wouldn't be also turned to stone. Other than earth elementals. Any suggestions?
Edit: I forgot to mention a few things. They're lvl 14, gestalt, and psionics and tech are available.

[avr]

Constructs, especially if they're already made of stone or similar. Undead are also immune to effects which require Fort saves unless they effect objects; not sure whether your area does, but at the very least incorporeal undead shouldn't be affected.

With the right amulet exploring the area would be very possible. Someone else might be doing that.

A quick search suggests that many outsiders are immune to petrification.

[deuxhero]

Search d20pfsrd for immune petrification and filter to bestiary results only.

Animated statues are a good option.

[CoI]

It does effect objects, and drains magic so items won't help for long. But I'll do that, I didn't even think of just searching immune petrification. Thanks.

[Scott Wilhelm]

Under Freedom of Movement, you aren't exactly not petrified, but you can still move normally, says my PFS community.

[Scott Wilhelm]

You can't be Petrified by a spell while you are under the effects of a Polymorph.

[Scott Wilhelm]

Antimagic Fields would squelch the petrification effect. So, say a Monk had some boxes that were glyphed with major glyph of warding, and the spell glyph were antimagic field, they could break open the box then enter the field for some hours at a time.

An Arcane Archer could fire arrows imbued with antimagic field into the petrification zone.

[CoI]

It's an area many miles in radius. As they get closer to the center their various energy sources get drained faster and faster, and they need to make their fort saves more often or lose dex as they turn to stone. It's been doing this for several thousand years, creating it's own ecology and effecting the evolution of creatures in and around it. For example several orc tribes living in the outskirts have been developing resistance and have gained a natural stone skin and natural armour, as generation after generation adapted.