To unlock and obtain the Voodoo Doll passive item, you first need to craft a legendary item called the Sacrificial Ball. This item cannot be found directly; instead, it is created by evolving another item.

Follow these steps:
Get the Spiked Ball: First, you must acquire the Spiked Ball weapon during a run.
Get the Dark Ball: Next, you need to adquire the Dark Ball in the same run.
Evolve the weapon: Upgrade both balls to level 3 and do the evolution.



Any curse ball works, it doesn't have to be this one. Darkness and ghost also work. I used this ball and it appeared to me.

Unlock the Voodoo Doll: Once you have the Sacrifice Ball, it will appear when you level up if you have room for passives. Everything must be done in the same run, as the dummy will only appear if you have the ball equipped.

To unlock these 3 objects is very simple, first, you must obtain any of the statues there (sword, bow or healer).



Once you have a few of them equipped, they'll appear as you level up if you have room for more passives. It's not necessary to have all three; one will do.
If you see that any of these 3 objects do not appear, try changing the statue in the next run.