One way is to make unholy frenzy a hero ability which requires level 6. That makes it automatically an ultimate ability and ultimates go through magic immunity.
If you dont want it to be shown as hero ability you can use a dummy ability which you give to your unit, and when this dummy abiltiy is being used you spawn a dummy caster with the real ultimate level hero ability unholy frenzy and force it to cast on the target.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory
I will be AFK for a couple of days you guys hold down the fort while I am gone. I will be checking in on my phone but that will severly limit me. Be back saturday!