"As High as Honor"
Due to its position in the mountains the Vale has long been thought of as unconquerable.
When Will House Arryn be Available as a Fealty?Edit
Disruptor Beam has announced that there is no plan to make House Arryn available as a Fealty any time soon. There is speculation that this may not happen until they are featured in the HBO television series more than they have been (ie. not until Season 5 is aired in 2015), however Disruptor Beam has neither confirmed nor denied any of this speculation.
Disruptor Beam (March 29th 2015; ☀https://disruptorbeam.com/forums/gota/viewthread/22713/P60/#139532) has communicated that they'll most probably include a future Arryn Fealty, but it requires a great deal of work and they are now focused in other parts of the Game.
Arryn VassalsEditOnce information is published in the game it will be shared here. For now, all we know for sure is the House Motto as it is published in the books:
As High as Honor
House Arryn's sigil is a white moon-and-falcon on a sky-blue field.
Characters that belong to, or have sworn fealty to House Arryn that are featured in the game...