Can someone without the Mark of Storm change the direction of an airship?

Question

In our Eberron campaign, airships are more common than usual. The bad guy in my adventure hides on an already flying airship, kills the pilot and crashes the airship against a castle next to the airship. A few seconds before it crashes, he jumps from the ship with a feather token.

Does my bad guy need a Mark of Storm for this? Or can anyone slightly change the direction of an airship by using his muscles for 30 seconds and crash it against a very large target? I understand that you need a Mark of Storm to communicate with the elemental in the core, but I am more thinking about a mechanical direction change which only uses the existing thrust and can only change the direction of the ship for a short time and for a short amount.

I don't want to give the bad guy a Dragonmark, since it would make it too easy to reduce the number of suspects to 12 half-elves in the town, where 11 will work for House Lyrandar and will very likely have an alibi.

Answer 1

Yes, you can control an airship without a dragonmark.

The rules for this are found in Eberron: Rising From the Last War on page 234, in the "Elemental Vessels" section under the header "Controlling the Elemental":

A character who is touching either the Khyber dragonshard where the bound elemental is housed or the magic item at the vessel's helm can try to communicate with the elemental, but with no guarantee of success.

A character can make a DC 20 Charisma (Persuasion or Intimidation) check to persuade the elemental to cooperate or demand its obedience. On a successful check, the elemental obeys the character for 1 minute.

It goes on to talk about using spells as another way to take direct control; a dominate spell can take over the ship automatically, even wresting control away from an active pilot, while charm bypasses the Charisma check but can't override the pilot.

The referenced "magic item at the vehicle's helm" is the wheel of wind and water for an airship; other kinds of elemental vessels may have different helm items. (Lightning rails in 3rd Edition had "lightning reins" that the pilot used to control the bound elemental, but for some reason all reference to that item has been removed in the current edition; it simply says the pilot controls the elemental without describing the helm item.) If not using the helm, the required direct contact with the khyber crystal is more difficult than it sounds, as the crystal is typically sealed in a metal casing in a containment chamber accessible only though locked and trapped doors (described in the "Freeing the Elemental" section immediately after the quote above).

So yes, in extremis, with a strong will, anyone can temporarily take command of an airship or other elemental vessel, provided the pilot is out of the picture; but it takes powerful dominate magic to take control against the wishes of a conscious and active pilot. Assuming that isn't an issue and this bad guy can make that quite difficult check (or you, as DM, just decide they can for the purpose of the story), they can take control for one minute, which should be plenty of time to do something terrible, if they picked the right moment to act.

Answer 2

A Mark of Storm is generally required to pilot an airship

The descriptions in Eberron: Rising From the Last War are clear that a Mark of Storm is required to pilot an airship, as shown in the following quotes, among others:

Lyrandar Airship Operation (Ch. 4)

A dragonmarked heir of House Lyrandar must pilot a Lyrandar airship, channeling the power of the Mark of Storm through the wheel of wind and water that controls the vessel.

Wheel of wind and water (Ch. 5)

When mounted at the helm of an elemental galleon or airship, this wheel allows a creature that possesses the Mark of Storm to telepathically control the elemental bound inside the vessel.

However, as described in the section on elemental vessels in Chapter 4, any effect that can take control of the elemental bound inside the airship can allow someone to control the ship. Darth Pseudonymn's answer covers this option well, so for my answer I will cover a different option:

Piloting a ship isn't the only way to move it

Just like with a mundane sailing ship, there's lots of potential ways to make an airship go where you want it to without being able to pilot it – especially if where you want it to go is down. For one example, suppose that the airship is flying directly over the castle, perhaps a scheduled flyover as part of some ceremony. If the BBEG were to kill the pilot, the vessel would presumably continue flying on its current course. Then, the BBEG could destroy the Khyber dragonshard that binds the elemental powering the ship, causing the ship to fall out of the sky directly onto the castle. (In fact, if the ship's elemental was bound against its will, it might even agree to assist in this endeavor.) This can all be accomplished without even using any magic (excepting the feather token required to escape safely), which in turn means that your players won't immediately have a short list of suspects who could possibly have pulled off such a stunt. And of course, an airship crashing during a ceremonial flyover is exactly the kind of dramatic, pulpy, action-heavy story hook encouraged by the Eberron setting.

If the airship isn't flying directly over the castle, perhaps the BBEG can "ask nicely" for the pilot to steer it in that direction before killing them and then proceeding with the plan outlined above. (The BBEG could also wave their feather token around, implying that they merely wish to jump off and land in the city, which might make the pilot more willing to do it than if they realize the BBEG's true goal.)

Of course, there are also magic means to forcibly move the ship. For example, with some generous interpretation Control Winds could "steer" the ship crudely in any direction, including up or down, especially if there is no one at the helm to counteract the effects of the wind.

Answer 3

Canon seems inconsistent on this

There are separate statements that seem to imply this is impossible, and others that suggest it is not, plus older canonical statements that are very explicit about it being possible but also seem to have been ret-conned.

5e statements suggesting a Mark of Storm is absolutely necessary

Eberron: Rising from the Last War states pretty unequivocally that the Mark of Storms is required to operate the wheel of wind and water that controls an airship:

A dragonmarked heir of House Lyrandar must pilot a Lyrandar airship, channeling the power of the Mark of Storm through the wheel of wind and water that controls the vessel. […]

Only a dragonmark heir with the Mark of Storm can use the wheel and command the bound elemental.

^{(Eberron: Rising from the Last War, “Lyrandar Airship: How It Works,” pg. 234)}

Wheel of Wind and Water

Wondrous item, uncommon

[…] allows a creature that possesses the Mark of Storm to telepathically control the elemental bound inside of the vessel.

^{(Eberron: Rising from the Last War, “Magic Items,” pg. 280)}

5e statements suggesting a Dragonmark is “just” extremely helpful

But then it seems to contradict itself on a number of points. First, there are also physical control surfaces:

A standard airship (at least as far as standards have been defined for this relatively new creation) looks simi­lar to an oceangoing ship but is rigged with control fins and rudders rather than sails.

^{(Eberron: Rising from the Last War, “Lyrandar Airship: How It Works,” pg. 234)}

It’s not at all clear how much control these control surfaces actually provide—they seem unlikely to be able to overpower the might of the elemental controlling the ship—but it certainly is something.

More importantly, the norm for bound-elemental vehicles is that non-dragonmarked characters can interact.

A dragonmarked heir at the helm of a vessel can com­mand the elemental easily. Without such a pilot, it's very difficult to control the vessel. A character who is touch­ing either the Khyber dragonshard where the bound ele­mental is housed or the magic item at the vessel's helm can try to communicate with the elemental, but with no guarantee of success.

^{(Eberron: Rising from the Last War, “Controlling an Elemental Vessel,” pg. 234)}

Making sense of the 5e statements

It isn’t clear to me if the rules for the wheel of wind and water are supposed to supersede the “controlling an elemental vessel” rules, or if manually communicating to the elemental remains an option even on a Lyrandar airship. Since it’s unclear, you can and should, of course, choose to interpret it the way that makes your story workable.

And if it does apply to airships, it’s a great possibility for you—elementals do not like being bound, and might happily comply with a plan that could see the elemental’s freedom. It might even comply with a plan where its “freedom” comes in the form of death, if its destruction came with the destruction of those who bound it and benefited from its suffering.

If not, though, there’s always creative sabotage—which will likely have to involve releasing the elemental at some point, since if the elemental is forced to resist crashing, it will almost-certainly succeed over anything anyone on the ship can do to oppose it.

3.5e statements explicitly confirming un-’marked airship pilots

Finally, note that many of the details of elemental vessels in Eberron: Rising from the Last War represent something of a ret-con for Eberron, from 3.5e’s Eberron Campaign Setting:

House Lyrandar operates elemental flying vessels (usually utilizing bound air or fire elementals) to make rapid air travel possible across Khorvaire. Built in Zilargo, these vessels can sometimes be found in privateer hands, but the pilots of Lyrandar are renowned for their skill and expertise.

^{(Eberron Campaign Setting, pg. 124-125)}

Here, there are privateers—unaffiliated with House Lyrandar and therefore almost-certainly lacking a Mark of Storm—who operate airships. This seems to contradict the description of the Wind Whisperer Lhazaar Principality that

includes a number of half-elves with the Mark of Storm—foundlings with no tie to House Lyrandar. The Wind Whisperers want to obtain airships by any means necessary.

^{(Eberron: Rising from the Last War)}

In Eberron Campaign Setting, the Wind Whisperers per se weren’t discussed, but non-Lyrandar airships certainly existed, including within the Lhazaar Principalities.

Conclusion

Anyway, long and short of it is, for your own game, you can choose your own canon. There have been canonical statements that seem to nix the idea, but there have been other canonical statements—even within the same book!—that support it. The 3.5e canon is even rather explicit about non-Lyrandar airships, to say nothing of piracy and hijacking of Lyrandar ships. So there is definitely room for this story in Eberron canon, at least for some definitions of that canon.

1. _{Wayfinder’s Guide to Eberron is also 5e content, but it’s Unearthed Arcana-tier content (“aren’t officially part of the game”), and moreover is largely replaced by Eberron: Rising from the Last War. I haven’t doubled-checked that publication for statements on this subject, but even if it had some their canonicity would be doubtful.}

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Many thanks to Ryan C. Thompson and Darth Pseudonym for pointing out many crucial details in Eberron: Rising from the Last War that greatly improved this answer.