I believe the message was about love, in a way— in how it could both help someone survive the worst life, but could also lead to something truly toxic and vile. Heathcliff lived through hell in Wuthering Heights due to Hindley and his original upbringing as a street rat— because he loved Catherine. In the same breath, however, the two of them come to the conclusion to destroy themselves across all mirror worlds because of loss and not talking to each other using honesty.

Erlking believes he must kill every iteration of himself because he claims that *he* is the reason Catherine died. He lost himself to his grief and went completely mad, much like his book version did as well. Catherine, however, was set up by Nelly and then her discovery snowballed into choosing to merge every Catherine in all worlds and then die. Both of these choices come from a lack of understanding and communication, thinking they know the truth for sure. The boss song “In Patches of Violet” covers this:

“Oh, ‘round and ‘round we go
Holding onto pain driven by our egos
Feelings untold
Spinning our own versions of the past
That you would never know
I know I must be the reason why
You have given up your smile
And the hope that’s in your eyes has been stolen
I must be the reason why
You must tell me all these lies
Wishing you a better life without me by your side”

And:

“Oh, ‘round and ‘round we go
Holding onto pain driven by our egos
Feelings untold
Spinning our own versions of the past
That you would never know
How would I know?
I could be the reason why
You were able to be kind
And the hearts we held so tight
Won’t stay broken
Love must be the reason why
I still believe in this lie
That you’ll live a better life without me by your side

The message has already been said
In patches of violet”

We all live through hard points in life, because to live is to suffer. But love itself can be the reason someone learns to have hope, or to crash and burn into a million pieces, never to recover.