Kory will not spawn until the enemy base is at 70% or about 700k hp. You have a lot of time to ramp up Worker Cat levels.
Strategy 1 (cheese)
Requirements: You only need Li'l Wall Cat but you should probably take some high damage cats unless you wanna wait a really long time. No powerups needed. Done with all EOC treasures and level 20 cats. Do not use LD cats, shockwave cats or extremely fast cats (due to a known rage glitch)Spam Li'l Wall Cat as soon as the level starts, do not slow down, your Li'l Walls will slowly push towards the enemy base. Use your cat cannon as soon as it charges for the first time, and DO NOT use it again. Eventually, your Li'l Walls will make it to the enemy base. Wait for the peons to stack up, your Li'l Walls will no longer be hitting them due to their short range, but they will be hitting the base. If you hit the cat limit, don't worry just keep spawning Li'l Walls, the cat limit will not pose a risk here. When it's clear there are no more enemies spawning due to the enemy limit, you've already won. Keep up your spamming and slowly but surely their base will be destroyed. However this takes a very long time, so just spawn in some strong cats to destroy the base quicker.
Doge, Snache, and Those Guys will be spawned frequently the start of the battle. Spawn a few Wall Cats to stall them and to fill up your wallet to the max. Once your money is maxed out, start sending out Dragon Cats. Keep spamming Dragon Cats only until the enemy base reaches 600,000 health, where you can start spamming Sexy Legs for extra support. Once the enemy base's health reaches 500,000, Kory will appear. Keep spamming Dragon, but not Sexy Legs. Along with Dragon spawn in Valkyrie and Mythical Titan to support. Once you have killed Kory, spawn in everything at once so the base can be destroyed faster.
If you do not defeat Kory fast enough and he reaches your base, do not worry; as a last resort, once Kory approaches your base/lose too many Dragons, save up money. Once he starts hitting your base, spawn in Bahamut to finish it off. It should work if you have dealt enough damage.
If you have Ring Girl Cat, you should have no problem at all; 2 of them stacked and at lvl. 30 (27 should be enough) can kill Kory by themselves by simply attacking first, knocking him back, and attacking again when Kory is back, repeating the process; due to their long time between attacks and the pause after attacking, Ring Girl Cats will never attack too early because of peons nor too late and always attack again when Kory is back, but before he does anything, making this unit perfect for dealing with Kory. However, this strategy requires a high-level Ring Girl.
All you need is 2 research combos Sm and Ramen lvl. 40
Constantly spawn ramen and then you win.
Strategy for higher stars
For 2 And 3 Star do the same exact thing as strategy 2 and Possibly advance the strategy with anti shockwave ubers or Kotasu Cats True form which can negate shockwaves entirely.
For 4 Star it is a totally different story. You will need Miyamoku Musashi to help you out since he is one of the only 4 cats in the special and rare category to be immune to shockwaves. (The others being Li’l Lion, Akuma Lion and Zamboney, they can also help greatly on 4 Stars flame caldera.) You should also use tanky, cheap and spammable cats that can tank Kory's shockwaves.
Line up: some good cats for combos, Awakened Bahamut Cat (30), Li’l Eraser (40), Ramen cat (45), Maximum the fighter (45), Riceball cat (30) Miyamoku Musashi (28).
Battle: Stall with li’l Eraser cat until you get Max money. Then spawn a couple of Ramen cat and maybe maximum the fighter. Also spawn Miyamoku Musashi. Once Kory comes out keep on spawning Maximum and Ramen. If Miyamoku Musashi dies then that’s alright. Keep on spamming. once Kory comes closer spawn A.bahamut. If Kory is pushing too much spawn riceball cat for emergency. Once Kory dies you’ve won and officially completed Volcanos Volkano!
- If you have li’l Lion or Zamboney you should replace Riceball cat with either one of them.
- Only spawn riceball cat for emergency. He can survive 1 hit from the shockwave so use that to your advantage.