This is a rather good story so far. I'll keep my eye on this.
There were a few errors that I saw. I'll point them out by chapter.
Before I point out each error, I just want to talk to you about commas and full stops. Throughout the story you make sentences go on and on because of commas. Go through each of the long sentences that contain commas, and if you can, break them up into smaller sentences with full stops. This makes it much easier to read.
Chapter 1
1. entered Rilly nose... Rilly should be Rilly's.
2. In the second paragraph, you had capitals for the words coming after commas. You should remove those.
3. Also in the second paragraph, you switched to present tense when you said "where are they now". Stick with past tense.
4. Picking off enemy's... enemy's should be enemies.
5. but the were taller... Drop the but. Also, the should be they.
Chapter 2
1. the wind is his face... is should probably be in.
2. stood on there hooves... stood would be better off as standing. Also, there should be their.
3. maybe the just toying... Drop the.
4. creatures drew there weapons... there should be their.
5. could see there fingers... there should be their.
6. "the sergeants warthog" Whispered Rilly to himself... This bit of speech should be on a new line and read, "The sergeant's Warthog," whispered Rilly to himself.
7. un-conscious Drop the hyphen and make it one word.
Chapter 3
1. "Go on kill me then" announced Rilly. You left out punctuation at the end of the bit of speech. Because you ended it with a variant of 'he said', end the speech with a comma: " Go on, kill me then," announced Rilly.
2. Rilly closed he eyes... he should be his.
Chapter 4
1. on where its inhabitants have been... It should read: in which its inhabitants had been...
2. food had past his lips... past should be passed.
3. decided to brake in. brake should be break.
4. plan the will... the should be that.
5. Everyone laughs. Keep this in past tense. laughs should be laughed.
Chapter 5
1. Don't forget to include punctuation at the end of a bit of speech. You left it out quite a few times in this chapter.
Good work so far, keep it up.
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