Talk:Relena's 3rd Challenge!/@comment-217.211.169.29-20170124175434/@comment-29349735-20170124183006

It has to activate first, which happens at the listed chance (30%) at the beginning of your turns. Once it activates, Ammy gets a little shield icon under her. Unlike nulls, counter activations can stack.

When an enemy attacks Ammy when she has this shield up, it consumes one stack of this shield. The damage drom that attack is reduced by 90%, and the attacking enemy instantly takes 1000% of the damage it would have done withoug this reduction. This applies to skill danage as well, though EH wave is immune.

It's actually a bad skill in PvE since it can cause you to unexpectedly kill things you want to save for overkills, but the chance of this happening is low if you are careful. It's a neat trick in pvp, even though it's not reliable.