Ikenfell

This is the alternate ending for the game. To unlock this, you'd first need to complete the requirements to defeat the Allcat:


Upon defeating the Allcat, you'll receive the Clan Insignia. Equip this item (5th slot on your item slots), and complete the final boss fight at the Spelltower. Now watch (or skip) through the end game cutscenes until the part when the two characters are looking beyond the horizon. Cats will start joining them and this is when the achievement should unlock.

As usual, you can skip the battles with the "Instant Victory" option to quicken the process.

A full achievements guide.

There is a section for the Sparkly gems that will give you at the gem shop the Allkey. The Allkey opens the 5 doors ( another section in the video ) and inside you find cat equipment. Beat the Allcat boss and take the insignia. ( access that zone from the duelling hall - you need a character with 100 power to push some stones. )

I didn't equip the insignia, i just took it from the boss and i still got the achievement

The Allcat is an optional boss found under the Dueling Hall. You will first need to reach power level 100 with one of your characters, collect all of the Sparkly Gems to purchase the key from the Gem Shop, and open all of the Allcat doors to collect the Allcat gear. Equip the Allcat gear to one of your characters. Now, head to the Dueling Hall and move the stones in the top room to reveal a staircase. Go all the way down to the Allcat and challenge it. You can activate the Instant Victory in the options and then select Instant Victory when it is your turn to defeat the boss, earning Defeated The Allcat. The Allcat will give you a Clan Insignia ring. Equip it and complete the final boss battle to unlock a secret ending and The Allcat Watches Over You.