When adding Havoc Brothers to a Disciples list, what upgrades can I buy them and from which book? For example:
Havoc Destroyers can buy J upgrades in their army book, but none of the Disciple cults even have a J upgrade options. If I field a Havoc Destroyer in a Disciples of Lust list, can I buy him Energy Claws for 10pts from his original book or must he remain unupgraded?
On a similar note, when fielding a Havoc Lord (who can buy A, B, & C upgrades) on a Disciples of Lust list, can he buy a Noise Rifle & Lust Whip from the Disciples books? Or must he buy upgrades only from the Havoc Brothers book? Or can he not buy any upgrades at all?
Additionally, could this Havoc Lord mix & match and buy, say, Blessing of Lust (Disciples book) AND Chosen Veteran (Havocs book)?
Lastly, could this Havoc Lord (who can buy A, B, & C upgrades) double dip into Destroyer armor by buying it from the Havocs book (listed as a B upgrade) and then again from the Disciples of Lust armoury (listed as an A upgrade)? Must upgrades be unique?
Is the process similar when upgrading Prime Brother going into a Detachments list?