Protection from protection from evil: how to kill unicorns

[ChudoJogurt]

So in my campaign a BBEG necromancer is sieging a magical unicorn forest.
Unfortunately for him, the gorram unicorns have a constantly active Magic Circle Against Evil, which means that no undead can even try to attack them with natural weapons.
... How can he bypass that defence? Is there something that allows undead to bypass the protection from evil?
The only thing I came up with is grabbi g skeletons and zombies and arming them with weapons, but thats weaksauce.

I want allips, shadows, shades... All them cool undead, that mostly come equipped with natural attacks.

So... How can I set it up so that the necromancer guy can get his minions to be useful against those pesky horny horses?

[Doctor Despair]

Necropolitan Changelings with Racial Emulation so that they count as the humanoid they're emulating for the purposes of all effects.

Intelligent undead with the Human Heritage feat for the same reason

Edit:

Flying undead that drop boulders on the forest until they surrender

A spellcaster that uses Necrotic Cyst to encyst and control living creatures to attack the forest and/or sabotage the defenses

[Cortillaen]

Are you talking about the "no nongood summoned creatures can enter the area" bit? And if so, are undead created through Animate Dead, Create Undead, and similar spells and abilities considered "summoned creatures"? They always struck me more as "made".

[Thurbane]

Yeah, PFE only blocks contact from Summoned creatures. Unless the undead are from a Summon Undead spell or similar, nothing prevents them attacking. PFE will, of course, provide it's numeric bonuses against attack from evil creatures, assuming the undead are evil.