Anima Sola will always target Dark Esau if he is present.
While Dark Esau is chained down, using Anima Sola again will release him and cause him to charge directly at Tainted Jacob, damaging and burning enemies in its path. This will not use up additional item charges.
Dark Esau deals no contact damage to Jacob while chained down.
Enemies other than Dark Esau can also be released. This will not cause them to do anything special.
If The Visage's mask is chained down when it runs out of HP, it will outright die instead of becoming temporarily inactive, leaving only the heart to be fought. It is unknown if this is a bug.
If Mom's Heart/It Lives is chained down before it can spawn the Eyes at the beginning of the fight and is damaged enough to advance a phase by the time the chains break, the Eyes will not spawn.