Rulings

• 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.2014-11-24
• For the "Dragons" ability, you decide whether the creature with flying will fight the target creature you don't control as the ability resolves.2014-11-24
• Each Siege will have one of the two listed abilities, depending on your choice as it enters the battlefield.2014-11-24
• 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.2014-11-24
• Each of the last two abilities is linked to the first ability. They each refer only to the choice made as a result of the first ability. If a permanent enters the battlefield as a copy of one of the Sieges, its controller will make a new choice for that Siege. Which ability the copy has won't depend on the choice made for the original permanent.2014-11-24