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If i were to choose a keeper of secrets as my lord choice, can i use ambushing units... it states in the BoC army book that any beast general can ambush....
A Keeper of Secrets cannot even take Unliving Idol. Also, if a Daemon Prince were given the Unliving Idol rule, he still wouldn't gain the Ambush rule which mean the Prince cannot carry the Brayhorn.
In other words, when it comes to choosing a Beast general, it's a choice between Ambush and Ld9.
Use Light, Beasts, Metal instead of Heavens
NecroLords: Use at least one Death Mage
Brets: Use Peasants&Damsels
Skaven: Don't use Skryre SAD