Official rule text
101.4 There are two advanced types of wormhole: delta and gamma. These wormholes follow all other wormhole rules. a The delta wormholes are present on the Creuss Gate system tile and the Ghosts of Creuss home system tile. b The gamma wormholes are present on the wormhole nexus and can be discovered during exploration RELATED TOPICS: Adjacency, Movement, Neighbors, System
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Source: Living Rules Reference and FAQ - Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 101.4