Dominion. This is why on Sel, people from different lands have different forms of investiture. People from MaiPon can forge, and people from Elantris can use Aons. They have 'dominion' over different lands.
The only known mention of Skai is in The Letter.
Unknown. It has however, been confirmed by Brandon that the Seons are splinters of Devotion created by that shard's splintering at the hands of Odium, it is logical to assume the Skaze have the same relationship to Dominion. 
Dominion and Devotion together make up the Dor. They did not work together, as Ruin and Preservation did, rather their Splintered remains merged in an unknown way and made the Dor. It is postulated that Dominion—meaning land, or country under control—is the reason only people of certain nationalities can access the Dor in certain ways. It is likely that being born in that country does not matter, it instead being related to feeling a devotion toward it. MaiPon people alone can use Forgery, and a map of MaiPon goes on the back of soulstamps. Only people of Aonic descent can be taken by the Shaod, but only if they are in Arelon at the time. Aons contain maps of Arelon as well.
|Characters||Raoden · Sarene · Hrathen · Dilaf · Galladon · Eventeo · Kiin · Iadon · Roial|
|Places||Opelon · Arelon · City of Elantris · Duladel · Fjorden · Teod · JinDo · Svorden|
|Magic||AonDor · Aons · Dakhor · ChayShan · Seons · Skaze · The Shaod · Forgery · The Pool|
|Mythology and Lore||Devotion · Dominion · The Dor · The Reod · Shu-Korath · Shu-Dereth · Shu-Keseg|
|Shards||Ambition · Autonomy · Cultivation · Devotion · Dominion · Endowment · Honor · Odium · Preservation · Ruin · Survival Shard|
|Planets||Ashyn · Braize · First of the Sun · Nalthis · Obrodai · Roshar · Scadrial · Sel · Taldain · Threnody · Vax · Yolen|
|Terms||Adonalsium · Sliver · Splinter · Realmatic Theory · Investiture · Connection · Identity · Fortune · Intention · Perpendicularity · Spiritweb|
|Worldhoppers||Hoid · Khriss · Nazh · Iyatil · Mraize · Vasher · Vivenna · Galladon · Demoux · Baon · Felt · Marsh · Nightblood|
|Other||Seventeenth Shard · Ire · Shattering · Letters · Silverlight|