Had a crash on the swords deal 3 to all as a minion was spawning due to a hit. Not sure if this is your problem or the mod of the boss's problem, but here's the crash log.

05:43:50.118 INFO ThMod.ThMod> ThMod : Card used : blackbeard:Sword ; cost : 1
05:43:50.150 INFO unlock.UnlockTracker> Already seen: blackbeard:SwordOfFire
05:43:50.151 INFO unlock.UnlockTracker> Already seen: blackbeard:SwordOfWisdom
05:43:50.157 INFO unlock.UnlockTracker> Already seen: blackbeard:SwordOfChaos
05:43:56.367 INFO basemod.BaseMod> publish on card use
05:43:56.367 INFO ThMod.ThMod> ThMod : Card used : blackbeard:HumongousCannonball ; cost : 3
05:43:56.517 INFO basemod.BaseMod> publishPostExhaust
05:44:02.068 INFO basemod.BaseMod> publish on card use
05:44:02.068 INFO ThMod.ThMod> ThMod : Card used : blackbeard:BlindAttacks ; cost : 1
05:44:02.100 INFO cards.DamageInfo> Damage Info calculation for Player is still in test
05:44:02.267 INFO cards.DamageInfo> Damage Info calculation for Player is still in test
05:44:02.434 INFO cards.DamageInfo> Damage Info calculation for Player is still in test
05:44:02.434 INFO helpers.AsyncSaver> Enqueue: qsize=0 file=preferences\BLACKBEARD_CLASS
05:44:02.438 INFO helpers.FileSaver> Dequeue: qsize=0 file=preferences\BLACKBEARD_CLASS
05:44:02.446 INFO helpers.File> Attempting to save file=F:\SteamLibrary\steamapps\common\SlayTheSpire\preferences\BLACKBEARD_CLASS
05:44:02.494 INFO helpers.File> Successfully saved file=F:\SteamLibrary\steamapps\common\SlayTheSpire\preferences\BLACKBEARD_CLASS
05:44:03.035 INFO basemod.BaseMod> publish on post power apply
05:44:03.036 INFO basemod.BaseMod> powers modified
05:44:03.268 INFO basemod.BaseMod> publish on post power apply
05:44:03.268 INFO basemod.BaseMod> powers modified
Exception: java.lang.ArrayIndexOutOfBoundsException: 2
05:44:03.653 ERROR core.CardCrawlGame> Exception caught
java.lang.ArrayIndexOutOfBoundsException: 2
at com.megacrit.cardcrawl.actions.common.DamageAllEnemiesAction.update(DamageAllEnemiesAction.java:86) ~[desktop-1.0.jar:?]
at com.megacrit.cardcrawl.actions.GameActionManager.update(GameActionManager.java:155) ~[?:?]
at com.megacrit.cardcrawl.rooms.AbstractRoom.update(AbstractRoom.java:279) ~[?:?]
at com.megacrit.cardcrawl.dungeons.AbstractDungeon.update(AbstractDungeon.java:2552) ~[?:?]
at com.megacrit.cardcrawl.core.CardCrawlGame.update(CardCrawlGame.java:878) ~[?:?]
at com.megacrit.cardcrawl.core.CardCrawlGame.render(CardCrawlGame.java:429) [?:?]
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:225) [?:?]
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:126) [desktop-1.0.jar:?]
Controllers: removed manager for application, 0 managers active
Game closed.