If we toggle the first, can we still have the procs from Black Cleaver ?

muramana is magic damage thus no

Black Cleaver procs from basic attacks and physical damage, so it should.

the real question is, will hydra/tiamat proc black cleaver?

That's why it's kind of unclear ; it adds magic damage to your attacks, so does it still proc BC ?

It adds magic damage to your physical damage so therefore the physical aspect is still there and yes it procs with autos

Black Cleaver is procced by physical damage AND basic attacks, so yes.

This isn't DotA there are no orb effects it won't cancel BC's effects on your AAs.

Ok thanks, just making sure.

I tried a fun build with Jayce yesterday on PBE : Mercury/Tabis, BC, Manamune (muramana), BT, Sword of the Divine, and Frozen Fist.

It's fun as hell, you do your W in Cannon form : max attack speed, then you do sword of the divine all that with Muramana toggled, it does like 800 damage a shot.

You heal like crazy because of BT, you can poke all day and when you attack someone you freeze them.

Also Manamune fills pretty fast because you can just switch stances all day and it costs no mana.