I was thinking about the various keywords with side effects (which are the ones that people build a deck around - there's no purpose focusing on Destruction magic, for example) in the game, and it struck me that, even though there are three main victory types, almost all of them focus on tower destruction.
There are only two I think where this is debatable.
Unliving: These cards almost split their effectiveness between tower construction, destruction, and resource accumulation. They have lots of attacking cards like Earth Eater, Clay Golem, Iron Golem, and Dragon Golem. They have lots of construction cards like Mud and Rock Elementals, Titan's Right Arm, Stone Golem, and Reuse the Rubble. They also have good cards that could be useful for resource accumulation decks - Obsidian Gargoyle, Titan's Heart, Titan's Head, and Water Elemental.
Brigand: Some might say that Brigand are good for resource accumulation decks. This is sort of true, but though their +/- stock abilities are useful, they have only one card that modifies any facilities, which is extremely important for that kind of deck.
So out of 11 keywords you could use as the centre of a deck, all 11 of them can be used for a tower destruction deck, and only one is useful for tower building, and only one (or two) is useful for resource accumulation. When thinking about introducing new keywords, it might be worth keeping in mind that there aren't any that are focused on tower construction or resource accumulation. Just a thought.