Thank you all for the suggestions.
Spirit Bonds could be an interesting addition, I'll see how to implement it
Eidolon of Countless Battles seems a bit underpowered here, not having auras. Nonetheless, it is cheaper than
Geist-honored MonkRibbons of the Reikai kind of scare me, I would prefer not to draw too much, to avoid discarding too much
Lingering Souls is good for its flashback ability but with a total cost of 5 mana gives me 4 spirits, while with 3 I can have three, which seems fine as well
Feel free to correct me, these are just my thoughts