Tessebik was a planeswalker from Dominaria who ascended when the Mending occurred. Masrath is a cool-headed person, who is hestant to take risks.
He was a school friend of Masrath, who often was able to persuade him to find excitement and action together. When they met again on their home plane, they decided to travel to a new plane that neither of them had been to before, Ravnica. They would each spend a few days exploring the lands, assimilating creatures and phenomena into spells, and seeking out new forms of magic native to that plane. Then they'd face off right there, on that plane, to see how sharp each of them had become in the nine years they had spent apart.