Anime Crossover: Starting with an Infinite Dragon God as a Mount

I was transported to the world of High School DxD and obtained a god-level achievement system.
Just as he was considering how to achieve his goal, Orpheus suddenly spoke up.
"Let's have a baby together."
[Ding! Congratulations, host, you have completed the Rainbow-level achievement, "Ophis actively invites you to have a baby!"]
[Congratulations, host, you have obtained the achievement reward: The Tree of Kabbalah!]
The Kabbalah Tree, the Ten Primal Elements, the Four Worlds, the Twenty-Two Paths, and the Three Pillars!
Crown, wisdom, understanding, compassion, strictness, beauty... a kingdom!
Activity, formation, creation, outflow!
"Divine Armor, Tenth Grade! Spiritual Rank Reversal, Tyrannical Duke!"
"This ending, I will never accept, I will never allow! Let it flow throughout the entire universe, my dominance, my reason! Let all things restart, let eternity return!"
"..."
Orpheus looked completely innocent: "I just wanted to have a child to defeat the Great Red, why did it turn into...?"