The premise of the setting is that long ago the surface of the earth became extremely hostile and uninhabitable, forcing humanity to seek refuge under the sea. Initialy humanity was under the rule of the legendary, despotic and technologically advanced "Geneticiens", but an alliance put an end to their empire.
Since then most underwater stations are still isolated and vulnerable to pirates, surviving as best they can - or not. Large nations have risen, but conflicts plague the oceans, and ontop of its widespread misery humanity faces a new problem as everywhere the human fertility mysteriously drops.
However, recently a cult which uses a mysterious ability called the Polaris effect, the Trident Cult, has managed to impose itself as a neutral force enforcing a fragile world peace from its neutral station of Equinox which has become a hub of trade, negociation and espionnage.
In this setting the players can be any sort of mercenary or scavengers, normal human or hybrids who do not needs a breathing apparatus in the water, independant or in the employ of the Trident Cult, facing giant underwater creatures or trained soldiers.
The 1997 and 1998 editions have percentile-based rolls and tend towards "simulation" with many specific modifiers. It is difficult to evaluate just how advanced or complex the rules are, but it states clearly on the back of the subsequent third edition of the game:
- "Making a new start, this new edition includes a completely new set of rules, more straightforward and flexible."
The third edition has a system based on the use of a d20, and on top of a basic ruleset has many optional rules along with some advanced (even more optional) rules which go into more complex details for those who wish.
The rules are the biggest change between the two first and the third edition, although the third includes many extra descriptions which make the book more than twice as thick.
There exists an alternate "third edition" which only existed on the internet, but in contrast to the published third edition it supposedly pushed the simmulationist aspect of the rules even further.