I'm new here, But I have an idea for a Karzahni and for events that lead to year 3.
The idea is that Karzahni did some More or less immoral experiments with elements that had terrifying results. And when Makuta, Ekimu and The Elemental Gods find out They almost instantly banished him from the island. This happened before the Matoran were even made.
Later he found a new island to continue his experiments on the elements, life and time. But with the power of his mask he saw something Dangerous coming or may be coming, but in any way he will not allow even the possibility. His mask not only showed him what would happen but also the solution. It showed Karzahni the only way to stop this danger is by combining the power The Elemental Gods by combining The Elemental Gods themselves in to one being. The problem is he can't ask them for help or make new Elemental Gods. He can steal their power, but one step to the island would be immediately detected by the The Elemental Gods.
So He began to observe the island from afar. And when he saw the Matoran he was not impressed, but when he saw the Toa and their strong connection with The Elemental Gods. he wanted to make beings like them, so that he can use their strong connection with The Elemental Gods to drain The Elemental Gods of ther Elemental power.
Karzahni started right away. A few years later he made the first race with a link to the elements, the Skakdi. Although they were physically stronger than the Toa, their connection to The Elemental Gods was weak, they could only cover the surface of their body with the element and maybe even move the element if they were very concentrated. They were a failure.
My sketch of Vezok, Zaktan and Hakann (I'm sorry for the bad image quality.)
After a few years, he made a new race the Vortixx, they had a better connection with The Elemental Gods and were more intelligent than the more warrior like Skakdi, but their connection is a little better than the Matoran and not even close to the connection that Toa have. They too are a failure, closer to the goal, but still a failure.
Then after the Vortixx he tried to improve the Vortixx and the Skakdi, who began to fight between one and the other to prove which race is better and worth living on the island. Karzahni did not care about their war, even though he liked the chaos that the war had caused. With experiments he found new things such as Protodermis, a teleportation machine, crystals that can hold elemental energy .... With Protodermis and crystals he made 6 prototype Gauntlets which can Absorb elemental energy and control it. But they did not absorb elemental energy directly from the gods. And gave them to the Skakdi. He made a lot of Protodermis tools and crystals, but none of them was a success.
After a few years to the present, he found a flying city away from the island with violet Matoran liveing in it, they were far away from the reach of the gods. "Great" he thought to himself, and decided to kidnap all the Matoran in the city to experiment on them and to make his own Toa. He took some of his '' experiments '' and immediately left in the direction of the flying city.