So, I'm bored and I want to talk about the potential of having Zhengui and Hanyi helping us in fights and duels, and what respective roles they may have.
Zhengui
Zhengui is a special Xuanwu, and even in yellow, he has extremely potent defensive capabilities as well as decent healing, AoE's, and offensive tools. However, we learned from Xuan Shi and our own research that Xuanwu have potent environment control abilities. These environmental control abilities are already somewhat manifesting themselves with Zhengui's ability to spontaneously create and manipulate roots as well as his ability to use plant life in order to increase his senses.
With Zhengui's ascension into the green realm, I foresee that these abilities will increase dramatically. But... this has already been discussed pretty much ad nauseum. So I'm going to move on to what Hanyi could possibly be about and then move on to how they could synergize with each other.
Hanyi
We know, regretably, less about Hanyi's type of spirit than we do about xuanwu. It's theorized that she is a Yukinko, or basically a child that sometimes accompanies a Yuki-onna (which is the type of spirit that Zeqing is theorized to be).
However, we do know two techniques that Zeqing had which she might have been teaching Hanyi, the "Lonely Winter Maiden" and the "Frozen Soul Serenade." Given that there were a couple of scenes last thread which seemed to depict Hanyi's training which indicated that she was competing with us to see who could be better at the "Frozen Soul Serenade" it would stand to reason that Zeqing was teaching Hanyi at least that song.
But now it's time to enter prediction and supposition! If Hanyi was to grow to be similar to Zeqing in ability, then there are a couple of things we can predict. First off, we can predict that Hanyi will be able to create and generate a blizzard, likely imposing penalties to people caught in it. Furthermore, it is possible that Hanyi could develop the ability that Zeqing showed during our first tribulation where she froze our ability to use qi. Which could express itself as increasing the qi costs of using techs? I don't know for sure. Additionally, it is likely that Hanyi can use LWM and FSS.
This would make her more of a DPS / Crowd Control individual. Someone who locks down an opponent and then kills them while they are locked down. It is highly unlikely that she will be as tanky as Zhengui, but it exchange she will likely have better offensive capabilities with some different forms of Crowd Control.
Assemble!
Should we be able to bind Hanyi, which is not guaranteed, then we will have two spirits who could be powerful combatants (assuming Hanyi also reaches the green realm). The problem, then, is how they would work together. Having a spirit that uses fire for his area of effects and a spirit that uses cold/winter could make it difficult for both of them to work in tandem.
However, I don't think it would be that big of a deal. Hanyi might be able to drag people over to where Zhengui is located and then Zhengui would be able to better deal with the opponent, or provide a solid defensive line that Hanyi can retreat behind. Zhengui's size will make a very large piece of cover for Hanyi to dance around while she batters her chosen opponent with frigid qi.
All in all, I expect Hanyi to dish out the damage and prehaps lure people into combat against her and Zhengui, while Zhengui provides the defensive abilities and environemental control to assist in dealing with the opponent's damage.
Also, if we want to stick to seasonal themes, Hanyi could represent Winter and the biting chill while Zhengui can represent the growth and destruction inherent in summer (droughts and fires for destruction with flourishing forests for growth).
Miscellaneous
When researching Yuki-onna and Yukinko I found an interesting tidbit on Wikipedia about Yukinko. That there are legends which say if someone can withstand the ever increasing weight of a Yukinko, they will be greated great strength. Given our choice of giving Hanyi a piggy-back ride, it seems that we are in for an interesting time.