Ah, these interesting creatures. Pack hunters, strong legs and weak arms. They're small miracles.
Despite being pack hunters, it's not uncommon to see a lone one meandering about, implying their natural shyness to sentient prey might not extend to less intelligent meals.
However, despite their inclination to fly literally everywhere, one must assure they train their legs somehow, and it's likely this is their most vulnerable moment. After all, they take great pride in being a rare underground, yet flying, hunter, thus losing their biggest advantage (airborne mobility) is a great hit.
Of course, maybe their constant flapping and adjusting is enough training. Either way, these leathery beasts make great pets due to their shyness...
Just never ever have more than one over. They love flanking.
AND THEN BEGINS THE HUGGING.
Oh the creaky, warm, leathery hugging. It's awful!

Note: this isn't anything I invented. It comes from a game called Deadly Rooms of Death!
http://forum.caravelgames.com/site/wraithwings

I wanted to do a little more, and my next piece will be a wraithwing with more modesty and pride. Why not!

Things gone wrong:

• Inconsistency between wings and body
• Legs look beefy, but irregular in length.
• Fingers. UGH, fingers.

Things not gone wrong:

• Feet, wing structure, leg muscles, beak.
• Pat on the back.