The Serpen House is considered the weakest among the houses in terms of prowess. True, their poison is deadly, yet, that's their limit.
Overconfidence had blinded them from expanding their foundation, unlike the Drago House that integrated within them the tamification on clothing or their evolving powers with the new generation.
That's why the Serpen House has always resorted to trickery and deceiving.
There's one rule that special to them in the world of Spirits, don't trust the serpent people. But they don't need trust. They can play behind the shadows, winning without fighting.
That's why Teren has to destroy them with the most bullish tactic. His Spirit of Healing is one of the greatest counters known to them.
Their poison is a sure-kill, degrading the Spirit within, yet slow-acting depending on the will of the person.
It's not about the physique of a person that matters, it's about their spirit of will.