The Jeh ancient snake advanced to the Diamond Rank slightly ahead of the Three-Headed Crane Phoenix.
The Jeh ancient snake's Diamond Level skill, [Damage Conduction], is a unique defensive ability that helps teammates share damage.
This skill allows the Jeh ancient snake to use its physical body to absorb damage that its companions would otherwise suffer—a self-sacrificial protective ability.
While such an ability is indeed useful in battle, under the current circumstances, the Jeh ancient snake can only protect the Three-Headed Crane Phoenix.
Shifting the damage away from the Three-Headed Crane Phoenix and having the Jeh ancient snake bear it instead doesn't contribute much to the combat effectiveness.
After all, if the Jeh ancient snake is heavily injured and loses its combat power, the Three-Headed Crane Phoenix alone will struggle to defeat powerful enemies.