The balloon belongs to a local family of traders who fled over the forestcliffs. (Madenifel would like to commandeer this balloon, but has no idea how to operate it).
If the party lands here, no challenge roll is required.
Sentinel Shells
Imperial sentinels are elite Mazrian soldiers encased head-to-toe in gleaming bronze-and-silver plate armor, with helmets shaped to cover their jackal heads. However, these two “sentinels” are actually elus—octopuslike monsters who wear the armor and use their amorphous tentacles to approximate the motion of a Mazrian soldier’s arms and legs.
Depending on what questions the players ask you, their heroes might notice the following oddities about the "sentinels":
They carry light wicker shields. Real sentinels carry heavy bronze shields. (The elus aren’t strong enough to hold heavy shields.)
They don’t respond to any hailing signals or usual communication. (The elus only speak the Antediluvian language.)
They don't seem to be good at their jobs. Real sentinels guard powerful Mazrian officials, or are sent on dangerous missions. These ones are just standing at a ruined skyharbor.
Encourage players to ask questions about the sentinels from the perspective of their heroes' origin, calling, and lore. A Mazrian would easily recognize these oddities. Heroes with backgrounds in combat, like Champions or anyone with weapon lore, might also notice that these elite soldiers don't seem very elite.
Once the party disembarks, the “sentinels” beckon the party past the ruined marketplace—always keeping one span or so ahead of the PCs—and toward the Chief’s Mansion, where an ambush awaits.