Type of abiltiies
There are several different types of abilities: Activated, Triggered & Passive, as explained in
the rules here. Knowing that might be helpful when making a suggestion.
Notice that there is nothing that forbids us from giving creature 1 the ability x, and letting x be a passive one, and at the same time let creature 2 have the same ability x, but as an activated ability instead. While this is a
possibility and could be done, it is rarely seen in a good game since it makes the whole system chaotic and harder for the players to learn.
I'm against letting one and the same ability show up as
different types within the same faction. If it's passive on one creature, then it should be passive on all other creatures of that faction that also happen to have the same ability. When "porting" an ability from one faction to another though, it makes more sense to also change it's type: It changes the nature of the ability very much and it also clearly shows that the ability is a foreign element within the (second) faction. An example of when that could be done would be if we portrayed an Undead or Possed Elf, that belongs to the Undead faction. It could very well have an ability that is normally associated with Gaia only, but with a different type and/or cost in order to balance it out for being in the undead faction in the first place.
Keyworded vs Custom
There's yet another important distinction between the abilities. Some abilities would be frequent and seen throughout the game. Others not so at all, and maybe only seen once or twice in the whole history of the game.
Common abilities should all be
keyworded. An example of this can be seen on
http://mtg.wikia.com/wiki/Keyword_Abili ... e_Keywords
Keywords makes the game easier to play in several ways and also saves a ton of card text space for us. An example of a keyword ability from MtG is "Flying". If you know how to play MtG, you are very well acquainted with what that means, as it has been around for a very long time and is well memori zed by every player.
It might be an idea to suggest keywords as well for an ability if one imagines that it will be a common ability.
Custom text abilities lack keywords: They are very specifically designed for one card and usually one card only.
Unique vs General
Lastly, some abilities really should be unique to a given faction. This is a designers decision that I think we should make to give each faction more character and asymmetry, a clearer identity. There is nothing that forces us to do it like that, but I myself believe that it's the proper way to go.
Exactly which these unique factions should be isn't set yet. In best case scenario some of them are connected to the faction identity and it's lore. As an
example it could be argued that "protection" could be a keyworded unique gaian ability. It captures much of their spirit.
All unique abilities do not have to be obviously related to a factions background - explaining them with lore and re-theming their keywords to better fit a faction is easy if we're creative and really want to.
While unique abilities would be given on a per faction basis, the general abilities should not be understood as abilities that are given to
all factions: A general ability is just any ability that is not exclusivley given to one single faction. It might be given to two factions or maybe all five for that matter (flying). It may however be distributed differently among the factions, even if it is general, so that for example Gaians would have few flying creatures (flying = general) while House of Nobles have many.