Exhaust to enter a Resolve Test against another character. If successful, choose a League on the map that the targeted character must travel to before he may resume his Quest. As his encounter each day, the target may make a Resolve Trial difficulty 7 to dispel the effects of this Art and resume his Quest.
Geasa is the plural of Geas (or geis, pronounced gesh), which Wikipedia defines as “an idiosyncratic taboo, whether of obligation or prohibition, similar to being under a vow or spell.” Like many of the Arts in Arcadia, this one corresponds to a cantrip or spell found in Changeling. This is a cantrip of the Art of Sovereign, as the icon on the above card indicates (see more on this in this post of darkyeoman).
With the Art of Sovereign one can control other people. Other Arts in Arcadia of this type are Protocol (in The Wyld Hunt), which forces any other person to follow nobles’ etiquette; Dictum (also in The Wyld Hunt), which forces a commoner to obey the commands of the noble caster; and Weaver Ward (in King Ironheart’s Madness), which prevents someone from entering a particular place or (as it is used in Arcadia) from acquiring a certain object. As several of these examples illustrate, the Art of Sovereign was long a well-guarded power of the nobility, who used it to control commoners, though some commoners have learned something of this Art too, to the dismay of the noble houses. (Keeping this in mind, you could decide that only noble Characters should be allowed to use Sovereign Arts in Arcadia, or come up with good story how a commoner might have learned this Art).
The Changeling rule book (page 185-186) describes Geasa, a cantrip of the Art of Sovereign, as follows:
When this cantrip is used, the power of Glamour is employed to direct a person upon a task or quest. This quest must be fulfilled to the letter, or the target suffers some kind of curse (designated at the time of casting). The target need not know what lies in store for him if he fails to complete the Geas, but the anxiety of knowing can be worse than the punishment.
The other use of this cantrip, called Ban, forbids a target from doing something or engaging in a specified activity. The most common use of this cantrip is the exile-Ban, which forces the target to leave a specified area and never return (or suffer the effect of the curse). A Ban can also be a forswearing of a certain activity, such as smoking, killing another changeling, etc. Certain forsworn quests and oaths are Geasa of a sort, and need no caster to initiate (the oathtaker’s will and desire are initiating the cantrip). […]
A Geas can be long-term (“Fight injustice whenever you face it.”) or short-term (“No one may move until I finish singing my ballad.”). The extent and power of the Geas (and the curse) are only limited by the number of successes at the time of casting.
Keeping this last point in mind, if you use 10-side dice for Tests and Trials, you can decide that the power of the geas depends on the success of the Resolve Test against your opponent: for every success above your opponent’s, you add 1 to Resolve Trial he needs to make to be released from it.
There is another type of Geas in Arcadia. As mentioned in this quote, oaths are “Geasa of a sort”. One of the oaths discussed in Changeling is “The Oath of the Accepted Burden”. This is how it is described (on page 211):
Lay down your burden, that I might take it up. The road is long, and I swear I shall bear it for you, until all roads end. I shall [the actual task is named here], else may the road cease to lay beneath my feet.
Superficially similar to a geas, this oath is a promise to perform a certain deed. The nature of the deed itself is irrelevant; it could be anything from a kiss to retrieving the still-beating heart of an enemy. This oath is always made to another, and is made to verify that a task that he desires will be performed. When these words are spoken, a Willpower point is gained by both the oathmaker and the one to whom the promise is made. If the oath is not kept, each loses two Willpower points.
Sounds familiar? Here is Pilgrim’s Burden, a Waylay from The Wyld Hunt:
Have you ever wondered why you would even think of continuing to lug that burden onwards when it becomes inconvenient? Why can’t you just leave it behind? It is because when you fail the Savvy Test, you have taken the Oath of the Accepted Burden, and now are forced to complete the pilgrim on behalf of the person you encountered. Oaths are not taken lightly, as we have seen, and you lose Glamour when you break one. But since this oath is a bit like a geas, it is not easy to break to begin with.