OH MY GOD. my beloved game. I'm not even kidding I genuinely spent hours upon hours playing this in year six
thank youuu.
As far as I remember, from the old guide on scratch (now deleted)
After you become a warrior, talk to Moonheart and she'll ask if you want to hear the story of Mosskit. When she's finished, there will be a red X at the fireclan border. You have to click on it and put things from your inventory on the X to try and get her back. Some things will work, others won't! When she comes back, talk to her, then lead her through camp to Bramblestar. If you have above 70 experience you will be named as leader after that cutscene. If you don't, you have to grind out the xp or the bad ending happens I think. If you know how to get to the cold stone then the Place of Cold Waters will give you your nine lives if you click it!