How about a skeleton Behir? It retains its grab and rake abilities (since those are exceptional abilities that augments its attack), so it's definitely quite nasty. It's not quite 14 HD, but it'd be a pretty intimidating and cool foe.
Alternately you can just go with something like a dragon; lots of natural attacks, and although they lose their flight, spells, and breath weapon they're still pretty fearsome just in that regard. Adult Black is exactly 14 HD.
Not bad. It could have been a giant behir, raising HD to 14,and stats,too. :)
The Giant template doesn't actually raise HD, just the CR of the creature. Of course you're the GM and you're free to tweak monsters however you wish.
more specifically it states
With a ritual requiring 8 hours, an undead lord can animate a single skeleton or zombie whose Hit Dice do not exceed her cleric level. This corpse companion automatically follows her commands and does not need to be controlled by her. She cannot have more than one corpse companion at a time. It does not count against the number of Hit Dice of undead controlled by other methods. She can use this ability to create a variant skeleton such as a bloody or burning skeleton, but its Hit Dice cannot exceed half her cleric level. She can dismiss her companion as a standard action, which destroys it.
So, either a 14 HD skeleton/zombie or a 7 HD variant skeleton/zombie. When I saw the title of the post I was going to ask if there was a gp limit, since one of my favorite skeleton builds uses several variant options. They are pricey but nice.
Once I saw it was the minion of an undead lord the relevant options drop quite a bit. I will look and see if anything jumps out.
I was able to find the following:
Each of these is 14 HD
Svathurim Skeleton
Rukh Skeleton
Sleipnir Skeleton
Zombies are a bit trickier because they get bonus HD based on their size.
Each of these have 14 HD
Brontotherium Zombie
Megalania Zombie
It might be easier to look though the druid animal companion list, pick out an animal that gets a bunch of natural attacks, advance it using the monster advancement rules and then apply the skeleon or zombie template based on what you're looking for.
You probably want to focus on animals and monsterous humanoids, since they are less likely to have abilities that get lost being turned into a skeleton or zombie.
most of the variants are probably not worth it since none of them are going to be so awesome as to make up for the 7 HD you lose in exchange.