The various emissaries of the gods of Runescape each offer players the opportunity to join a particular faction (including the Godless). Each of these factions seems to represent to me a particular facet of culture in the real world, all of which tend to be present in each culture to one degree or another. Refer to the "Book of the Gods" for more information on each faction. If I just tick them off, the idea becomes much clearer, so let's get to it.
Seren's faction represents the Goddess of the Elves, and therefore seems to me to suggest the need of each culture to insulate itself from the efforts and ideas of other cultures, whether creating extreme isolation and even xenophobia, or whether the culture is exceptionally porous and tolerant. Even an insular culture may be relatively benign, as it governs itself in response to internal dynamics, and incubates new and characteristic ideas. (That has no bearing to my Wikia, does it? P;D)
The cult of Zaros, the Empty Lord, seems to represent to me the tendency of a culture to undermine some or all of the abilities of the people through a form of atrophy. In a healthy culture, individuals exchange the ability to take care of their business in their own way, and the group tends to handle these problems in ways that have been defined as culturally and socially valid. Those individuals who continue to exercise their individual abilities in a culturally invalid way are censured, shunned, or otherwise punished as being "wild" or "uncivilized". But this process can continue until the strength of most of the people has atrophied almost completely. If the culture finds itself developing in an unhealthy way, it may not have enough individual virtue left to avoid a cultural collapse, environmental disaster, or conquest by another culture.
Saradomin represents the culture's need to protect, defend, and nurture its principles, and to look after the welfare of its adherents. It will also tend to proselytize, protect the welfare of adherents of other cultures, whether or not this tends to bring converts or not, and oppose cultures it sees as inhumane. Cultural values tend to be broad, vaguely defined, and constantly being argued and reinterpreted by various parties.
Zamorak's cult represents a culture's inherent and necessary respect for the realities and contingencies of existence within a reality which is not exclusively controlled and defined by cultural attitudes. A culture which faces constant changes and threats to its existence tends to emphasize individual excellence and strongly-held values for as long as that set of attitudes meets the necessities of the moment -- and then just as quickly casts them aside when needs change drastically, or emerging problems have been allowed to accumulate too long. Thus, the culture is in constant "management-by-crisis" mode.
Armadyl's cult emphasizes the need to enforce and constantly reemphasize the values it is charged to uphold. The rewards to individuals for representing these values properly, and the punishments to be meted out for those who betray central values, can be breathtaking in their magnitude, force, and swiftness.
Bandos' cult represents the inherent element of conflict within a culture, as well as between one culture and another. Cultures tend to change the circumstances in which they find themselves, rather than alter their tenets to better suit the circumstances. In a culture such as this, conflict is seen as a first resort, or even as the most preferred method of solving any particular problem. Bandos' cult tends to emphasize physical conflict, in contrast to other forms of conflict.
Sliske likes to see culture as a set of boundaries and limitations against which other persons or groups can be pressed. He and his followers operate in the shadows, manipulating others with both real and false cultural elements. This sort of conflict is rather more covert, but no less dangerous for all the harm that can be done. In all, this cult sees culture as a set of codes that can be "hacked", using confusion, deception, terror, anarchy, and strife to enable them to obtain what they want -- the exclusive end to which they apply their means.
The Godless are those who choose not to affiliate themselves with any of the above cults, and tend to succeed or fail on the value of their own efforts. Some are very successful, others do well enough, and others find themselves incapable of dealing with their problems without the patience and understanding of other Godless.
Disclosure: I have chosen the Godless as my faction. I stand by my choices, my values, and will be proud to own up to any perceived bias. "Man is nothing without the gods." But what are the gods without Man, or without men?
Guthix represented the tendency of a culture to be a singular form of continuity, alongside such features as object persistence, human memory, genetic and epigenetic inheritance, and various other forms of continuity. In contrast to some of the other positions here, it tended to emphasize the value of a culture's existence, and its need to preserve itself and its continuity as a primary value.