Creative writing fail

Ok, this is a piece of short fiction we "wrote" in class today. By saying "wrote", it actually means that 5 different people had a go on different sections of the story.
Try and see what is wrong with it - it should be quite obvious!

***

I am an invisible man. With my magic axe, I disappear behind my enemies' backs, trying to reach the orb of power before it slips away. Skeleton warriors and ents clash furiously, whilst I blend into their midst and head for my enemies. I see the orb of power hanging from his back. The undead general, proud and tall even in undeath, he marched with his troops, his orb glowing bright. I sneak towards him, trying to be as quiet as possible. The crunch of my feet on the dry leaves scattered around the graveyard is masked by the cracking of bone in socket as the skeletons mill around confusedly, trying to find the smell of meat that has awoken them. I am close now, the orb of power is mere feet away. I can feel its otherworldly power drawing me in, the world disappears, fading to white. My energy starts to drain away, I know I don't have much time. If I take too long I'll just collapse in a heap, pray for the scavenging skeletons that are getting ever closer on their quest for fresh meat.
In my peripheral vision my eye catches the undead general's rotting corpse as it plunders around the graveyard. "He knows I'm here" is the only thing that I must avoid. Be decisive, I told myself firmly. There is no room for uncertainty on the battlefield.
Gripping my axe firmly, I slithered forward silently, shrouded from the general by my axe. I held my breath, careful not to give away my presence.
Within striking distance now. I swung my axe high - and then I woke up. Feeling, once again, that I don't belong in this reality, that I shouldn't open my eyes to see through my window the tall buildings and barely moving cars in the streets. I know there is somone out there who needs to be saved from skeleton warriors.