Amumu + Frozen Heart doesn't take damage from minions
My friend figured this out, tested it many times and it works.
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My friend figured this out, tested it many times and it works.
+ 
Why not? It's just 100 armor. I don't think this is true.
That's why it's a bug-- it isn't supposed to happen. In regards to op: any specifics on how to reproduce, or any evidence?
You can ask a friend to try it yourself in a custom game. Tell your friend to stop your minions and you just need to let your friend's minions swarm around you.
I guess this'll be the thread that disables amumu due to a game-breaking bug lol
Have you tried this without putting any points into E?
If you get enough armor, it's quite possible that the minions' damage is being reduced enough that Tantrum's passive blocks it entirely. I can't remember if it reduces the damage pre-mitigation or post-mitigation.