MTG - Crossroads of Fate

Every cards in Magic: The Gathering always carry fragments of stories, and as Fate Reforged revealed, this spell is more than enough to tell us about the story why Sarkhan Vol traveled through time: 

This Black Spell define the epic battle between the two Dragon Planeswalkers, Ugin and Nicol Bolas

As for you players who hadn't experience the Time Spiral expansion, there are event called Mending. It's an event that changed the Multiverse and what it means to be a Planeswalkers.

As the battle took place before the Mending, here we are to see how fearsome Planeswalkers was. Planeswalkers are entity with virtually invincible power. Many refers to them as Gods, as they can even cause catastrophic disaster in a whim, just like what we see here: The battle of Nicol Bolas and Ugin, the Spirit Dragon.

After the Mending that took place in Time Spiral, Planeswalkers retained their power to travel between worlds, but in exchange of that, lose their god-like powers. They're now referred more as powerful Mages than powerful beings.

Those who survive the mending are limited on power, and those who survived the mending are turned to become the planeswalkers we see today.

If yo're wondering where this epic scale battle took place, you can see this card art of "Crucible of the Spirit Dragon" for reference:

more info at magic.wizards.com