Once you reach the quest that transform you into a necromancer, follow the path indicated.
Once you reach a room full of necromancer you have 2 options :
- Remove transformation and kill them all
- Ignore and open the gate.

To get those 2 hidden Mokoko on the right, you have to IGNORE and open the gate then kill the gatekeeper a bit later.
Once you killed him go back to the wall and you can now get those Mokoko.

2 hidden Mokoko to the east.
After transformed to necromancer ignore the gathering and open door to the east.
Go north and kill boss before elevator.
Go back south and kill mobs, pass thru door to the SE.
Loot 2 Mokokos

Just to clarify because the other two posts were very helpful but confusing for me.

1. Where seed number six is, the room before that is where the summoning is happening.
2. You pick up your necromancer outfit from the room across the hidden story pick-up.
3. You pick up the outfit and walk past the summoning and towards the next section which is is triggered after you open the door to the right and stand in the green box.
4. Continue on and kill the boss at the end of the walkway but then you can turn around and run back to where the two hidden seeds are located - the wall that blocked you will now be able to walk through and collect the seeds.

Again, just posting this to make it a little more clear because my ADHD brain needs hand-holding!