The reason Adrian suddenly appeared in a flash of lightning is due to the fact that the Tree of Life and Death activated one of its defensive functions to call upon its defender. Even though the Tree of Life and Death that was summoned is not the main body, it is still part of the collective consciousness that the real one has. The Three-Legged Golden Crow is also a divine beast which means that it could directly hurt the main body of the Tree of Life and Death.
It was not just Saena that was summoned because Adrian and Kimat were also called upon due to their connection. Adrian just had to confirm that he wants to be relocated and there he was on top of the Three-Legged Golden Crow. Kimat suddenly pounced while Adrian summoned Sirius to aid them as the enemy is a user of light elemental energy.
"Since when were divine beasts so easy to call?" Adrian muttered as he can feel that the Three-Legged Golden Crow is not a being that is part of this world as of now.
