I’ll get to this in canon eventually but Webcomic Time takes forever and I want to show off SOME history. So here’s some stuff on the First Dreamers and the Alpha Trio to tide you over until then.

The First Dreamers

Pictured above, the First Spawns VS the Present Day Dreamers

80,000 years ago, when the ancestors of modern day house cats started living in homes and barns, they also felt more comfortable with lowering their defenses and sleeping deeper than before.
Because of this, they had some of the strongest dreams compared to other creatures. Even compared to humans! They even had strange powers inside these dreams, something that no other creatures had in their dreamworlds
And something about their brainwaves made it so the barriers between their dreamworlds were super thin, and even combined in some spaces. But there was never a point that they would spawn in the same world together.
At least until the First 3 came around

The Alpha Trio

The original 3, their fur colors are the only thing that’s lost to history

These cats were the first 3 to spawn in the same collective consciousness that is now known as the Buffer Zone.
Their (translated) names were FROST, SPARK, and EMBER, and they were a part of the early bunch that had singular powers (Blue Ice, Yellow Lightning, and Green Fire respectively) with eyes that matched their powers. (their fur color however, is a mystery, it’s assumed they were tabbies or possibly solid colored, since domestication hadn’t happened yet)
It would take another week before more cats would start popping up in this world. But in the meantime, these 3 explored the area and came across one of the first Portals. As they all reached out to touch it, the portal shocked them, scarring their forearms and linking them to the Buffer Zone forever.
Because of that fateful encounter, these 3 cats are constantly reincarnated into other cats with powers to match, and are often the ones spearheading developments in the Buffer Zone.
It’s also a cursed mark. The Reincarnated Trios always correlates with the Monsters spiking up, and every Alpha Trio that has all 3 members reawakened tend to die within the year by a brutal Monster attack.
The last Trio (Lilly, Tamara, and Walter, from the 70s) barely lasted a month after being Reawakened, the quickest on record.

Since then, the Trio hasn’t been found. Which can sometimes happen, since only one or two could reawaken, or all 3 did but were so spread out that they were killed off individually without actually meeting up. Or even revealing their scars for that matter.
The last stretch before Lilly’s team lasted at least 60 years with no Alpha Trio Reincarnations found, and it was the calmest the Monsters had been in decades.