Shroud — An invisible defensive shield.
A shroud is a field of energy generated by a ship’s crystal power core. It is invisible and its purpose I'd to block enemy cannon fire. Airships will put in place their shroud when they may be going into battle. They are not kept put up as a matter of course.
"When a cannon blast struck the shroud, it illuminated like a hazy, spherical cloud flickering with lightning, absorbing the incoming fire and dispersing its energy safely before it could strike the ship. Shrouds were a strain upon a ship’s core, a tremendous demand upon the core’s energy reserve. One did not simply sail along with the ship’s shroud raised and in place." 
Mechanics / Technology Edit
Creedy did note to Grimm that the Predator's shroud is powerful for a ship of it's size. Certain, the ASA Itasca has multiple crystal power cores and can afford the energy budget for a more powerful shroud.
- "The largest part of a ship’s power budget was allotted to its Lift Crystals. Less energy spent on keeping the ship afloat meant more power that could be used for other systems. They could get more speed out of the etheric web by charging it more highly, increase the density of Predator’s shroud, and fire her cannon until their copper barrels melted."
Some shrouds are thicker, some are thinner. One can apply full power to shrouds, thus implying shrouds can be formed with variable strengths. There is a matter of deciding the energy budget tradeoffs between the shroud, lift crystal, trim crystals, weapon crystals, etheric web, etc. They can also be configured to be thicker in one specific area (Journeyman configures the shroud to be thicker on top to protect against the Mistshark's attack at the Habble Landing shipyard).
Other Details Edit
- At Folly's request, the "soul" of the Predator uses the ship's shroud to affix the red star that represents Ferus' collection aboard the Mistshark.
- When configured for speed, the ethersilk webs extend beyond the protection of a ship's shroud.
- Heat from enemy blasts can seep through the shroud and be felt by a ship's crew, along with the scent of ozone.
- Shrouds fail in a large burst of sparks.
- When struck by cannon, shrouds blaze with green light. When strained, shroud's illumination becomes dimmer, more translucent.
- It is not known how fast they regenerate after taking damage. This would be crucial in battle.
- Etheric webbing
- Etheric cannon
- AMS Predator
- ASA Itasca
- Airships Parts, Gear and Technology
- Albion Ships
- Francis Grimm
- Core Crystals
- Lift Crystals
- Mark IV-D Lift Crystal
- Leftenant Hammond - starboard gunnery officer
- Habble Landing
When the Predator is attacking the Auroran Cortez-class airship, it's stated that the Cortez-class airship has a thicker shroud.  When the Predator gets the Battlecruiser-sized, very efficient Mark IV-D Lift Crystal, Mister Journeyman states that they'll be able to generate a thicker shroud.