I will soon be DMing an Eberron campaign for my Dungeons & Dragons group. As part of the plot, I want a player or NPC to bind an air elemental to an elemental airship, and it may come up in the future. I recently bought the Wayfinder's Guide to Eberron, and I used an example from the book as an NPC (a gnome artificer).
Is there a specific ritual for binding an Elemental to an object or vehicle (e.g. lightning rail or something similar), assuming they already have the elemental?
The process of elemental binding is mentioned a number of times in the Wayfinder's Guide to Eberron... but no rules are described for how this is done.
Lightning rails and elemental airships are briefly mentioned in Chapter 1, under the heading "A Magical World" (p. 6):
Here are a few examples of how magic is integrated into everyday life in Khorvaire.
The lightning rail uses bound elementals to drive a train of carriages along a path of conductor stones. The rail links most major cities and is a simple way to travel long distances.
An elemental airship uses a fire or air elemental, bound into a ring that holds the ship aloft and provides motive force. The airship is a recent innovation that is transforming the business of transportation.
There's barely more detail about them (and elemental galleons) in the "Transportation" section of Chapter 2 (p. 46), but no mechanics are provided on how they are created.
Elemental binding is momentarily mentioned again in the description of the nation of Zilargo, earlier in the same chapter (p. 38, italics mine):
Noted for Gnomes, alchemy, education, elemental binding, entertainment, precious stones
In Chapter 3, the same nation comes up again in relation to elemental binding; the "Gnomes of Zilargo" section has a "Zil Schemes" table, and the first row provides a relevant character hook:
Your family is working on a new form of elemental binding, but they need Khyber dragonshards — lots of them.
Khyber dragonshards are described in more detail in Chapter 5 (p. 113):
Khyber dragonshards have a affinity for binding magics. Elemental binding — which is behind airships, the lightning rail, and elemental galleons — requires a Khyber shard to hold the elemental. Khyber shards are used for phylacteries, planar binding, any other effects that trap or manipulate spirits. Khyber dragonshards are also used for many necromantic rituals.
A later part of the same chapter mentions a relevant magic item, the wheel of wind and water (p. 117):
When mounted at the helm of an elemental galleon or airship, this allows a character who possesses the Mark of Storm to telepathically control the elemental bound into the vessel.
Chapter 6 is about Sharn, City of Towers. It provides a number of tables for use in quickly generating a basic story set in Sharn. The table "The Hook" contains this possible plot-hook:
The PCs discover a bound-elemental explosive device in their quarters. They have three rounds to flee or attempt to disarm the device.
And finally, there's one last mention in Appendix A: Further Reading, under the "Eberron Sourcebooks" heading (p. 165, italics mine):
Magic of Eberron (3.5E): In addition to presenting new arcane and divine spells, feats, prestige classes, and magic items, this book offers new options and infusions for artificers, explores dragon totem magic and the twisted experiments of the daelkyr, sheds light on the process of elemental binding, and touches on other types of magic present in the world.
I don't own this book, but it is likely your best bet for finding more information on the actual process of elemental binding. Of course, any mechanics from it that you wish to implement in 5e may require some changes in the process of converting it to a different edition.
As the beginning of the section notes, the Magic of Eberron book is available as a PDF from DMsGuild.com (as are the other 3.5e/4e sourcebooks mentioned, presumably).
That's basically every mention of bound elementals in the Wayfinder's Guide to Eberron. There are no mechanics given for binding the elementals, only interacting with those already bound and what they might be bound to. It directs readers to a 3.5e book for more details.
The original material lore from the 3.5 Eberron Campaign Setting states the gnomes of Zilargo are the ones with the knowledge to bind elementals to vessels and such. The book lists a feat, Bind Elemental.
The feat in 3.5 depends on the magic item crafting mechanics detailed in that system. Porting this entire system forward might be more trouble than it's worth. Coming up with a suitably expensive and interesting mechanic for your campaign could provide plot hooks and motivation to adventures to collect ingredients, knowledge, and equipment.
For reference, the 3.5 feat required of the character the ability craft greater wonderous items and be a 9th level caster. The feat involved casting the planar binding spell and added tens of thousands of gold to the cost of an item.
