When Valen fearlessly told the Elder to move away, Natha had to hold himself back from coming over and kissed the man right there and then.
But when Valen took the first step into the lake, he also had to hold back from yanking Valen away, taking the man into his embrace. He even gripped the little elemental bird tightly because of that, but the bird was also tensed from the atmosphere that it didn't feel it or let out a protest at all.
That was why he brought Eruha along; to hold his body. The vampire, from the moment Valen walked toward the lake, had stepped in the Lord's shadow to lock Natha's movement.
Because Natha, above everything else, had no confidence he could hold himself back from jumping into that lake and taking Valen away.