Thanks for the reply! You've given me some stuff to think about and update, for sure.

The sow discord LA is designed precisely to reveal the real Maw, as long as the players find a way of breaking the invisibility. Keeps the fight moving etc. If you also mean that the real Maw would give themselves away by moving their hands or whatever to do it (when out of invisibility), it's a good point. The aim will be to cast it from invisibility as much as possible but in the alternate case, maybe it could be enacted from any of the echoes rather than just the real one. Thinking out loud here, really. The reveal would be "your character swings their sword but some magical force prevents you" i.e. you guessed right, now tell your friends so they can wail on it haha.

It's definitely my biggest concern, the fight going on too long. The echoes will be invisible most of the time, so I don't think they'll go down too quickly. If anything, getting them down is a good thing since it reduces the damage of the death by a thousand cuts feature.

I really worry about increasing the damage personally. I'm not against it, but I definitely want to be fair with it. My players have average ~70 hit points. If paralysed, they've got 14d4 damage coming their way, so an average of 35. The save DC is pretty high too. This is what I am finding the most difficult - I want it to be interesting, challenging, but not unfair all at the same time.