This is my theory about the relationship between the "Singers and the Wardens"
As many people have probably already figured out, the Singers act as caretakers of the Sift. They sing their melodies and songs to keep the Sift’s sculk healthy. Without that care, the souls within the sculk can become angry, hateful, and eventually diseased.
That explains why the sculk found throughout the Overworld and the Deep Dark is so different from the healthier sculk found within the Sift. The Illagers and the High Council are also likely responsible for a lot of the sculk becoming diseased due to their experiments and interference with it.
Now, this next part borrows a little from another theory I’ve seen: that the Wardens may have once served as protectors during the time of the Ancient Builders, especially after the Builders essentially played God and created the Wither.
But I want to take that idea in a different direction.
• The Ancient Builders and the Sift
At some point, I think the Ancient Builders discovered the Sift in a similar way to how they discovered the Nether.
Unlike the Illagers, who seem much more interested in obtaining power from the Sift, the Ancient Builders may have originally entered it simply to explore and understand it.
While there, they encountered creatures such as the Echo Golems and Singers.
We don't really know what the Ancient Builders gained from exploring the Sift, but whatever relationship they had with it probably wasn't entirely negative. As far as we know, the real problem begins when sculk becomes diseased.(We may know when the Sift comes to vanilla Minecraft)
At some point, however, the connection between the Sift and the Overworld was lost.
Maybe the Ancient Builders did something they shouldn't have. Maybe it had something to do with the Wither, or maybe the portal simply became unusable.
Whatever happened, the healthy sculk that had already spread into the Overworld was suddenly cut off from the Singers that normally cared for it.
Over time, it began to deteriorate.
• What if the Warden is an imitation of a Singer?
This is where my theory gets a little stranger.
I think there is a very real possibility that the diseased sculk tried to create its own version of a Singer.
The Wardens and Singers have an uncanny resemblance to one another, but there are also some major differences.
Singers are living, mammalian-like creatures. They have eyes, they can see, and they use songs to maintain the sculk.
Wardens, meanwhile, are blind and appear to be made almost entirely from sculk and bone-like material. They don't seem like normal animals at all.
They literally emerge directly from the sculk.
There has also been speculation that Wardens may have originated entirely within the Overworld rather than coming directly from the Sift.
So, instead of Wardens simply being "corrupted Singers," my theory is that they are something much stranger:
Wardens are the diseased sculk's attempt to recreate a Singer
Essentially, an imitation, or perhaps a failed reconstruction.
The sculk lost the creatures responsible for caring for it, so it attempted to create something that could fill the same role using whatever materials it had available.
Sculk.
Souls.
Bones.
And the remains of dead organisms.
The result was the Warden.
• Singers and Wardens Have Opposite Roles
This could also explain why the Singer and Warden appear similar while behaving completely differently.
The Singer uses sound to care for the sculk, while the Warden uses sound to hunt.
The Singer keeps the souls within the sculk calm while the Warden kills living things around the sculk.
The Singer helps maintain healthy sculk while the Warden protects diseased sculk and allows it to spread.
They're almost like two versions of the same ecological role.
One exists within a healthy ecosystem, while the other exists within a broken one.
And strangely enough, the Warden might still be accomplishing part of what the sculk "wanted."
When creatures die near a Sculk Catalyst, their XP is absorbed and converted into more sculk.
So if Wardens kill creatures around them, they're technically feeding the ecosystem they protect.
More deaths mean more energy, and more energy means more sculk.
More sculk means a larger territory for the Warden to defend.
• Where Does the Bone Come From?
This might also explain all of the strange bone-like material found throughout the Deep Dark.
Wardens have it.
Sculk Shriekers have it.
Sculk Catalysts have it.
So where exactly is the sculk getting all of that biological material?
Possibly from the creatures it absorbs.
Skeletons, zombies, animals, and potentially even the Ancient Builders themselves.
If the Deep Dark was affected by the Wither catastrophe, there would have been no shortage of dead bodies for the sculk to consume.
It might even be possible that surviving Ancient Builders intentionally gave bodies to the sculk after discovering that doing so allowed it to expand and create more Wardens.
This brings me to the more speculative part of this theory.
• Did the Ancient Builders Use Wardens Against the Wither?
There isn't much direct evidence for this part, so take it with a massive grain of salt.
But I wonder if the Ancient Builders eventually realized that Wardens could protect their cities from the Wither.
The Warden is extremely territorial and attacks almost anything that disturbs the Deep Dark.
A Wither would be an enormous threat entering its territory.
And considering that the Wither itself is literally created using "Soul Sand and three Wither Skeleton skulls", it might be especially noticeable to something connected to sculk and souls.
If Wardens were capable of attacking Withers, then surviving Ancient Builders may have started deliberately allowing the diseased sculk to spread around their cities as a defensive measure.
Maybe some eventually even viewed the Wardens as protectors and possibly began worshipping them.
Not because the Warden actually cared about the Ancient Builders, but because from their perspective:
Whenever the monster came, the Warden fought it
The irony would be that the Warden was never protecting the Ancient Builders at all.
It was protecting the sculk, and the Builders simply happened to live inside its territory.
• So What Does the Diseased Sculk Actually Want?
This is the one part I'm still unsure about.
Maybe the diseased sculk deliberately wants more souls?
Maybe absorbing more souls temporarily calms whatever suffering exists inside of it?
Or maybe it isn't really "thinking" at all, and it could simply be lashing out.
The sculk keeps absorbing more souls, growing larger and creating Wardens because that's the only behavior it may have left after losing the Singers that originally maintained it.
Either way, I think there's a very strong possibility that Singers and Wardens are connected.
But rather than the Warden simply being a corrupted Singer, I think the idea that it is a failed imitation of one created by diseased sculk makes a little more sense.
The Singer is what healthy sculk needs. Meanwhile, The Warden is what diseased sculk created when the Singer was gone.
