Investiture Focuses

[Trusk'our he/him]

Invested Arts all have an Intent based on their Shard, which determines how that Investiture is obtained. However, I think each system also has something else- a Focus. 

The Focus of an Invested Art, well, focuses the Investiture, making it more efficient. 

Also, I think that a Focus for a system is based on the planet rather than the Shard- Odium's Investiture seems to share Roshar's Focus and Autonomy's systems of Aviar versus Sand Mastery and Starmarks seem to be different. 

Roshar's Focus seems to be gemstones, which naturally hold Invested Lights, can be grown by local fauna (which seriously aid in bonding Spren, something that is possible but difficult without a Gemheart), and can even help rececitate Deadblades enough to bond them. 

Nalthis's Focus is life. Awakening an organic object is orders of magnitude easier than Awakening something like a sword, and Lifesense works way more easily on truly living beings than Awakened entities (which requires the Seventh Heightening). Furthermore, using a portion of your own body, like your hair, can make Awakening cheaper. Awakening a Lifeless with their own Breath (using the natural Connections) is more efficient, making them more cognizant. 

Scadrial's Focus is metal. Obviously. Allomancy can draw Investiture from Preservation by metabolizing it, Feruchemy can use it as a battery, and Hemalurgy can use it as a scalpel. Pushing and Pulling on metals Allomantically is way easier than non-metals, probably because natural Connections are already in place. Metals shine brightly in the Cognitive Realm, likely because of their Connection to the system's Investiture. 

I would compare this to flowing water: a Focus is like water that's flowing downhill and has made troughs in a mountainside, making it much, much easier to flow through again. Trying to use Investiture without its Focus is more like trying to push water uphill- possible, technically, but horribly inefficent and requiring way more force to achieve. Maybe possible by getting so much water it can make a wave and splash upwards (Awakening metal or Pushing/Pulling on non-metals), but undesirable. 

Thoughts?