The famous O2 can only be reached if you
have obtained all shards, and beaten Miracle Matter after
obtaining them all! Through this, Ribbon and Kirby can use
a shard-like gun and head to dark star (which appears
after you beat Miracle Matter).
O2 at first, can be hard.
There is three different type modes of battle - the first
is where Kirby and Ribbon shoot at O2's eye. While you
shoot at his eye, he'll shoot out disc type ammo at you.
Once you've hit him enough, he'll sort of freeze and
you'll have to shoot his halo. Once his halo turns from
yellow to green to blue, to red you'll then get to hit him
at this real weakspot: his tail! His tail is a huge green
spikey thing, that will grow smaller each you hit it.
However, he will be shooting clouds of green gas at you
while you do this, so it's not entirely a free shot.
Overall, O2 at first will be a long battle.
Once you can pick up on the routine of fighting him, he'll
quickly become your easiest battle. Gotta dig that cool O2
music too!
