Just like the big Oondasta, he's got a Frill Blast, Spiritfire Beam, and Crush. Frill Blast will deal a large amount of damage to your active pet and swap it for your highest health pet. (Woo forced tank swap.) Spiritfire Beam is like a chain lightning, dealing moderate damage to all pets, and Crush is a single target attack.
It took me several combinations to find a group that worked for the fight, and ultimately, treating him like Dos-Ryga and opening with a Stampede-style ability worked best. Lil' Oon isn't particularly fast, so most of the pets I tried got to go first in a round vs. him.
Thlayli |
I started with the Tolai Hare after realizing flying pets were probably a bad idea (Spiritfire Beam and Frill Blast do additional damage to flyers). Sure, he's a critter, but Oon doesn't have beast abilities despite being one. He's got the Stampede I wanted, and he's wicked fast. Of course, being such a speed-heavy little rabbit, Oon's Frill Blast one-shotted him. This is not surprising: Frill Blast one-shots a lot of things. If you pop Dodge your first round, the Stampede will get off a bit extra damage, as well, because you'll just dodge the first Frill Blast.
Anapa |
A Frill Blast death pulls in the Anubisath Idol, since he's the highest health pet in this group. Even if the Hare dies from other damage, I swap him in second. I had included him for this fight because a) he's got a decent amount of health and b) he's got a wicked hard Demolish vs. Beasts. Stampede's armor break allowed the Demolish to hit basically for full damage, and as long as you don't miss, he's going to get in probably two, three if you're lucky and Oon misses one round. If you want to try for a chance to do a bit more damage before Lil' Oon eats him, you can try to get a stun off Rupture.
Bolts |
Once the Anubisath Idol is dead, Oon will probably be low enough for a mechanical with Wind-Up to finish him off, even though the armor penalty has worn off by now. I went with the Mechanical Squirrel; I know a lot of people like Brooms with Wind-Up, but the Spiritfire Beam does less damage to mechanical pets, so it's more likely to survive the fight on the back lines.
The first time I tried this combination, they one-shot Lil' Oon. The second night it took I think three tries, and I played a slightly more careful match (using Dodge and Rupture) to improve the odds of it going through. If you haven't got three strong mechanicals (I don't; I have three 25s, but two are middling), you've got other possibilities if you play towards what you've got that will hit him hard, debuff him, or doesn't take extra damage from his abilities.