Here we go, the first boss fight of KH:CoM and...it's the first boss of KH1...and it's not hard...like, at all. Use the event cards if you want, it'll help out in taking down the boss, so long as you don't sleight your cards to use Sonic Blade, it'll only hit once and it's better to just attack with your cards, why I have a 0 Blizzard in my deck I don't know, but, eh, it's not worth talking about. Also, bosses usually drop enemy cards (couple exceptions as in the next boss fight and the boss after you complete the next few floors and more exceptions after that). The Guard Armor card adds on increased range to attack cards for the next 30 or so attacks, not really all that useful.

Guard Armor difficulty: 1/10 (anyone can beat it on the first try if they're not mentally retarded)

Cards needed to open door: Green Card+Key to Truth (less info)