Instead, train your Orthrus up to adult. Then, hatch the two of them together.
Take that baby and train it up to adult or ancient. It's in the hatchlings that you have a chance to develop the best combination of talents from your pure Orthrus and your pure Crystal Butterfly.
Butterfly talents that you want to look out for are: Critical Hitter (+25 Critical) Defender (+30 Block) Element Shield (may cast elemental shield) Spirit Shield (may cast spirit shield) Lively (7% heal incoming) ...and maybe... Balance Ward (15% Balance resist)
From your Orthrus, you'll want to look out for these talents: Myth Giver (6% Myth damage) Myth Shot (6% Myth accuracy) Myth Trap (may cast Myth trap) ...and maybe... Pip O'Plenty (5% pip boost) Health Gift (+125 health)
You might need to hatch several times to get the best combination of talents. Take two great babies that are trained to adult or ancient, and hatch them together. Their children are the ones you will try to train up higher, like to Epic.
Hatching will cost you roughly 45,000 - 50,000 gold per hatch. Also, it will take a lot of pet snacks to train the babies. Start gardening for pet snacks. The best plants are: Evil Magma Peas, Couch Potatoes, Prickly Bear Cactus, Frozen Flytraps, and Maelstrom Snap Dragons. All of these drop megasnacks at elder. EMPs are crowns only. The rest can be gotten as drops (Couch Potatoes, in Grizzleheim), or bought at the Bazaar.