One of the new boss fights is in Bretta's house in Dirtmouth.

Great Slash stoped working after i installed the update

I think the 2nd Boss fight is in the White Palace

Where is the stag station ?

The 2nd boss is dd! He'll be in the secret room under the switch where you activate green liquid flow! Simply stand under it, and desolate dive/ descend dark.

Wow that's actually really hard to miss

The boss in Bretta's house seems to change everytime you rematch him, I think there might be a reward for beating him multiple times

The stag Station is next to the white palace ruins, go all the way right and there is a breakable wall. BOOM hidden stag station

Also, dont know if anyone checked inventory but next to the dream nail is a new item that explains how to fast travel using the dream gate

where 2nd boss?

first one is in Berettas house, you have to have fought zote in order to find the shrine under her house, second is the dung defenders secret room, desolate dive right under the switch for the acid just after the room you fought him in originally. you need the dream nail to fight both bossse

The Grey Prince changes the more you you beat and rematch him. He attributes to his title every time, on the 3rd rematch he starts spawning explosive enemies and by the 4th rematch he does 2 damage each hit.

dd is too ez if you just stay at right side