What is the point of Darktellarknight Batlamyus with the new dark rebellion dragon?

I saw a video about a Phantom Knights deck with the upcoming Dark Rebellion Xyz Dragon of the Four Heavenly Dragons and theguy was speaking about options to bring out with it, like Karmael, Evilswarms and Batlamyus...

What is the point on using Batlamyus? I get that the Tellarknigth XYZ monsters are really good but she can only summon on the opponent's turn with 7 Tellarknight materials.