The Devourer of Minds on Mercenary.

I can use this for Mercenary raise limit of Frenzy charges for my minions ??.

I don't think it will work, because they are your minions and not the Mercs. If the Merc has any minion skills probably will work on their minions, but not yours. There are some mods like this that share throughout the party, but I do not think this is one of them.