Allow me to note a dislike of the LA system as standard, especially with regards to things like this. I'd nerf the heck out of this template - perhaps grant it abilities that scale instead of a bunch of high-level at-wills - in order to make it a lower LA and thus significantly more playable. As it is, a character made with this template is going to hurt compared to a character without it. See, the problem with granting it LA +6 is that it doesn't have the staying power required. It has a Con penalty and no damage reduction, fast healing, or regeneration. All it can do is heal themselves 1d12 damage a number of times per day equal to their App modifier, and recover 2 ability point damage a similar number of times per day. Assuming a roll of 18, with the +4 modifier, that's still only six times per day to counterbalance the feviri being very fragile compared to other creatures of her ECL.
Clockwork Avalon - Updated 1/13/2015, home to my Dragon Realms campaign setting (and someday my Clockwork Avalon setting)