You have to know every Magic story to get this one.
Beginning in the Thran, some Planeswalkers choose champions to fight for them in an
enormous game of chess(or Magic).
Dyfed chooses Yawgmoth, the smartest of the Thran.
Leshrac chooses Lìm-Dûl, the greatest necromancer on Dominaria
Freyalise chooses Jodah, the most powerful mage on Dominaria.
Urza creates Gerrard, the ideal warrior to fight Yawgmoth.
Kristina chooses Taysir, the strongest slave in the Domains.
Taysir(post-ascendancy) chooses his daughter, Daria.
Tevesh Szat chooses Baron Calchexas Sengir, an immortal vampire lord.

The other Invasion Planeswalkers choose no one and stay out of the Planeswalker Games.
Most wallow in their own power, amassing obscene wealth, knowledge, and power.

Yawgmoth kills Dyfed, and takes his own mastery, now fighting for himself.
Freyalise’s champion Jodah defeats Leshrac’s Lìm-Dûl during the Ice Age.
Leshrac takes Lìm-Dûl with him and leaves Dominaria. Freyalise has no challengers for
thousands of years. The long-lived Jodah eventually succumbs to old age.
Kristina takes Taysir to Ulgrotha to fight Baron Sengir. She knows he will be a
Planeswalker, and hopes it will trigger the change. It does, and the Baron is all but killed.
Tevesh Szat, who the Baron believes to be the god of wealth takes him to
Dominaria before the battle of Jodah and Lìm-Dûl, where he founds the Cabal. After
unsuccessful revolution attempts, Calchexas decides he will wait as long as he has to till it is
safe.
Yawgmoth attempts to fight every Planeswalker at once. You know the story.
After the Apocalypse, the only Planeswalkers left on Dominaria are Freyalise and
Lord Windgrace. Lord Widgrace’s only attempt at a champion, Mirri, was killed by
Yawgmoth’s only attempt at a champion, Crovax during the Rath cycle.
At this point, Leshrac returns. Calchexas believes him to be his god of wealth, and
Leshrac, in need of a new champion, allows this. He takes him to the continent of Otaria,
where the Patriarch’s Cabal flourishes.
The only gods on Dominaria during the Odyssey cycle who seem to have any
power are Fiers(Windgrace), and Leshrac. Windgrace, finally entering the
games, is backing the barbarian Kamahl. Leshrac is backing the immortal Cabal Patriarch.
Freyalise has not yet chosen her champion. All that remains is for her to do so.

Sure explains a heck of a lot doesn't it?
The missing stuff about Taysir fighting the Baron is from the upcoming Homelands novel, which I myself am writing. (sigh) I am so proud.