Inside the palace, upon the throne.
With the palace gates firmly sealed, Orion summoned the Abyssal Dragon.
The Abyssal Dragon lowered its head, affectionately nuzzling Orion. Orion reached out and stroked the dragon's gigantic head, giving it two light taps.
"Xalathar, open your mouth!"
The Abyssal Dragon parted its massive jaws, and Orion tossed in a bundle of Legendary-level life essence.
"Don't let me down. Make sure you don't fail your advancement!"
Roar!
The only response Orion received was a deep growl. Immediately afterward, the Abyssal Dragon transformed into a flash of crimson light, returning to Orion's heart to advance.
For Xalathar the Abyssal Dragon, Orion's heart is the best training ground.
Once the Abyssal Dragon vanished, Orion pulled out the final white bone box, removed the chunk of life essence inside, and swallowed it in one gulp.