how the hell do pierce defense work???

[Dalapie]

i cannot shoulder bash bladestorm from destroyers, i cannot do it on blade dancers , how is this worth using in talents? 

[Zakaru]

It pierces blocks and counters.  That means KFM/BM blocks as well as the other melee classes counters while knocked down.

[Tteunaegi]

It also works against Sins Decoy as well.

[phinders]

I mean it tells you exactly what it means in the tooltip...

[Nachtdrache]

Resists/iframe mechanics do not count as defense for some goofy reason. Zakaru and Tteunaegi are correct it should affect

 

KFM counter

Assassin decoy standing and on ground

All classes ground counters

Summoner flower counter

Blademasters block

Destroyers shield

I'm sure theres more

 

It doesn't work on dodge abilities, typically Q+E abilities, Destroyer and BD spins, assassin C ability (if specced)

 

You can use knockdown on both the spinning classes .5 seconds after they start except for destroyers Q/red spin.