Oh, shit, I'm dumb.. that doesn't work with enchantments :DD
May 12, 2018 2:53 p.m.
The ability to choose Khans or Dragons is a replacement effect modifying how the enchantment enters the battlefield. Even if it is an artifact (via Mycosynth Lattice) or a creature (via Starfield of Nyx) you will not be able to make a second choice. If the Siege is an artifact or creature and has an ability that triggers from an itself entering the battlefield (such as Frontier Siege with Starfield of Nyx and Levitation and 2 other enchantments) it will trigger itself twice as long as you choose the relevant side with Panharmonicon out.