你五行为火,蛇毒大寒,自是克你 I tried googling this, but all that comes up is that it's a phase in the seasons. I don't think that's what it means in this context. I tried saying the venom is cold, but I feel like it describes the venom as physically cold rather than the opposite of fire. I want something that's more.....innate, I guess? My translation: Your wu xing is fire. The snake venom is inherently cold. Naturally it suppresses you.
You did get the inherent meaning correct, that is that something was suppressed due to a weakness to "cold" The closest concept I can think of is that of yin and yang, with reference to chinese medicine and food, describing things that are "cold" and "hot". However if the universe in which your story takes place is more based upon the five elements, (fire, metal, wood, earth, metal) when referring to wu xing, then you might want to consider leaving it as hot and cold. On another note, isn't it wu hang (行), as in five paths?
The pronunciation in this case is wu xing and not wu hang. Its to reference the 5 elements, fire, wood, water, earth, metal
I know what it is in reference to, but I always thought wu hang made more sense, but guess I was wrong. TIL
你五行为火 I think it means: Your element within the 5 elements is fire. You could just abbreviate it to "Your element is fire." and it should be fine. Second and third lines look fine to me.