Frontier Siege

For the "Dragons" ability, you decide whether the creature with flying will fight the target creature you don't control as the ability resolves.

The words "Khans" and "Dragons" are anchor words, connecting your choice to the appropriate ability. Anchor words are a new rules concept. "[Anchor word] — [Ability]" means "As long as you chose [anchor word] as this permanent entered the battlefield, this permanent has [ability]." Notably, the anchor word "Dragons" has no connection to the creature type Dragon.

The "Khans" ability triggers at the beginning of both your precombat main phase and your postcombat main phase. Unused mana is lost at the end of each step and phase.