The first brought the water of the ocean. He wanted the others to recognize his leadership so he would have complete influence over their lives and decisions and that they might go along with whatever idea popped into his head. 

The second brought the water of the stream. Being the most intelligent was hard. Each bad decision they made had a predictable calculated outcome that he saw from a mile away. But there was more of a dangerous outcome if ending up alone. He would not miss the chance. 

The third brought the water from the icy lakes. He was not from the area. He was curious about this ritual, and wanted to know if his lineage would give him some kind of a deeper understanding of what they would be dealing with tonight.  Perhaps he may even be acknowledged by an entity of nature.