Just for passing time, I think I got a grasp on what Lilith's Mega Umbreon might be like. Caz's idea might be different, but, I'm just putting my idea in place for the fun. I have no picture of it, except for the sprite.Looks crazy.
Here's what I think of it....
Type: Dark/Fairy
Ability:
Wolfsbane Aura (Reduces damage taken from Poison-type attacks to half. Sharply boosts evasiveness in Dark Crystal field and Misty Field).
OR, if voting for an already existing ability
Shadow Shield (Reduces damage from damaging moves by half. Sharply boosts evasiveness in Dark Crystal field and Misty Field).
Stats:
HP: 95
Atk.: 65
Def.: 110
Sp.Atk.: 60 -> 120(+60)
Sp.Def.: 130
Spd.: 65 -> 105 (+40)
Total: 525 -> 625 (+100)
Umbreons are known to produce toxic sweat as a style of smelly defense against threats, hence, it's only natural that it gains resistance to poison when it evolves as it itself produces poison. Thus, the reason for the new ability.
It's yellow colored patterns not only serve as scaring tactics but also the patterns glow-in-the-dark dimly but only when it attacks. It has a natural art of deception at night and in moonlight. Glow of it's rings is said to give it mysterious powers, possibly this mega form. Thus, it's only fair to say that it is highly evasive in misty and dark fields.
Moveset:
Throat Chop (Lvl. 9)
Dark Pulse (Lvl. 55)
Play Rough (Lvl. 29)
Moonblast (Lvl. 60)
TM - Dazzling Gleam.