u/Consistent-Chair

STEP 1: THE ITEMS
-Use Storage Locker to find Cat Rib, Cap and Bells, and Cancer. You can do act 1 runs on normal to guarantee a win. If you don't go where the quest item tells you to, you can do this indefinitely. Use a Soul Jar with a cat that has Repair to not let the storage locker break. Remember to equip items that give you rerolls so you can see as many items as possible for every run.

STEP 2: THE CATS

1. Equip a cat with Cap and Bells and Cancer, and bring Cat Rib along. Continue farming mutations until you get the ones you want. At the end of the run, swap Cancer with Cat Rib, keeping Cap and Bells, and get 3 copies of your mutated cat. This will also get rid of all the stat debuffs from Cancer.
2. Bring one of the mutated kittens along on a run, equipping them with reroll items like Clown Makep and Chaos Controller. Remember to always bring along a Cat Rib. Look for Skill Share. In case you don't find it, kill the cat and start again with its 3 clones.
3. Also remember this (from the wiki): "Cats taken on multiple adventures by using the Cat Rib will always be offered the same level-up abilities (including when rerolled), unless a new ability is chosen to replace an old ability. This can be important to take note of, as cats taken on multiple adventures with the goal of getting a specific ability will need to replace their abilities at least once each adventure"

STEP 3; THE FINAL MONSTER:

1. Once you get your Skill Share cat, kill them and get 3 clones.
2. Repeat step 2, looking for Goofball or Super Luck.
3. Because the first skill choice is not randomised, you can only get them on your 7th level up. This means you cannot upgrade Skill Share. Therefore, one last run will be required to do that.
4. You now have 3 cats with 15 strong mutations and the best passives in the game, who always pass them down. This is your forever starting point. You no longer need to breed new generations. Just put strays with them in a high stimulation room, and get as many non-imbred super kittens as you want. At around 60 stimulation, you'll get a clone of the original cat pretty much every day. When the original cats are about to die, just get another Cat Rib. You have solved the game. Congrats. It only took around 10 hours of grinding 😃