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I was building an army using army builder, trying to figure out what I wanted to play, and I noticed that there is a "mutate" selection, where you could give just about anything "exceptional size," or "acid blood," as an example. I don't see this in the codex, and I don't remember it being in the chapter approved books. Can anyone tell me if this a "legal" addition, or forgotten/amended rules from the past (like prior to the release of the 3rd edition codex). Thanks
"Exceptional size" and "acid blood" are legal mutations just like "hive node" and "weapon beast", to see what these mutations do see page 37 of the tyranid codex under "Mutation types" to see what rules you have to follow to mutate a tyranid into any of these read pages 36-37.
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