Special Nodes are nodes that contain one of the several possible types of nodes. They will give theater effects (battle effects) if there is a space battle on the system and also benefits to the one who has it's influence zone over the special node.
Unfallen get "System Effects" by vining their tendrils on Special Nodes.
Behemoths from the Supremacy DLC can make use of Special Nodes giving some usual point resources, Strategic Resources and Science Research Reduction Cost
A base of +50 , +50
and +20
from 'Basic Node Analyzer' (Behemoth Analyzers)
-2% /-3%
cost in a specific technological category alongside +80
/+160
by modules unlocked by Behemoth Analyzers, and Behemoth Advanced Climatology, respectively.
+1 of 2 types of Strategical Resources of the same technological level (provided that the technology to extract the resource is researched) and +25% Special Node Effect when oribitng by module unlocked by Behemoth Basic Climatology.
The Umbral Choir from the Penumbra DLC will have it's Home System set in one of these Special Nodes, and may also place Transmigration Beacons on these nodes which allows them to get the "System Effects" on their Home System, as well as migrating there. (unclear if it works on Rejuvenation Field)