If this were the case for No Man's Land, one could consider, mayhap, that the veins lead from the Gazebo of Equilibrium outward and towards the Capitols of each respective land; in concept, imagine that the Gazebo were in perfect balance (hence, equilibrium) betwixt the lands, and that a slight push in any direction should cause one travelling along the heat-veins to then flow toward the respective capitol. In this sense, the "entrance" were the Gazebo itself, and the exits were the respective entrances to each land, for a continuous flow toward each capitol, and that each scene towards each capitol were representative of greater influence of that land, such that the capitol were the most influential site within each land. I suppose that this were somewhat inspired of the second idea, but a solution if indeed one must consider No Man's Land and its many gateways.
If this were so, and contingent on Necrovion being closed and free from rulership, then should all assume that there is no possibility of Necrovion ever becoming open, or of one ascending of its throne? One thinkst that should such political upheaval arise, that the relative advantage or disadvantage should have been considered when mapping of these veins. In example, if such heat veins all did flow toward Deathmarrow, one could consider merely to taint of certain heat and release it along the vein to cause of change in Deathmarrow; Necrovion's capital may thus find itself the centre of the interplay betwixt lands seeking to spread of certain influence.