Are you sure it's extra bosses and not just how the trees get up and move during the final boss phase?

I have often seen it double, usually overlapping, I would say 20% of the games that I get that far it is double. I have seen it as two distinct bosses, yes, rarely.

I do think it is a display thing, you don't have to kill them both separately

I mean, yeah I don't have to kill each of them but I do have to dodge 2-5 times the amount of attacks lol

So I had 4 last time and i had 6 this time. I simply could not dodge enough of the circles and died. I think it is based on how many runes you have active. Each rune adds a mirror image of the final boss, which requires you to dodge that many more of his attacks. If you don't have something like freeze and infinite ammo, you better have some epic summons. You either have to stay our of range so he cant attack, or attack chain stun. No in between for more than 2 runes

Originally posted by Not Found:

...I think it is based on how many runes you have active. Each rune adds a mirror image of the final boss, which requires you to dodge that many more of his attacks. ..

Thanks for this, thought I was going crazy also.

This game is all about crazy synergies, but good to have a mechanic like that. Gives a potential reason to pro/con a shiny red upgrade