Egg Cauldron

The Egg Cauldron is a mini-boss from Sonic Unleashed, fought at the end of Tornado Defense Act I & II. It is a flying fortress armed to the teeth with aircraft and cannons. If Sonic & Tails are defeated by the Egg Cauldron, you will have to restart the whole act from the beginning.

Boss Guide
There is one primary way to beat this boss, and one secondary method that only works during Act I:

Method One: Wait until Eggman launches a full-scale attack. After defeating all of the enemies, the large access door will remain open a couple of seconds. While it's open, shoot it using whatever button is indicated. Repeat until destroyed.

Method Two: During Act I, it is possible to win the battle by simply surviving the onslaught of missiles and fighters attacking you. After the 2 minutes and 30 seconds timer is up, the fortress will incur an energy failure and fall out of the sky. However, this approach will NOT work during Act II. Allowing the 3 minutes and 30 seconds timer to reach zero here will result in the Egg Cauldron fully charging and automatically destroying the Tornado, costing you a life.

Trivia

 * Due to the mini-game Tornado Defense not being in the Wii version, this fight is skipped entirely.