The Eternal Fort is the name given to a highly elusive anomaly in Super Mario 64. It is generally believed to be an Anomalous Area of some kind, although due to it's anomalous effects on players, there is little to no concrete information on it.
The Eternal Star is believed to be related to the Eternal Fort due to their name, and the Eternal Star being the basis of many rumors regarding Super Mario 64.
The Eternal Fort is most famous for it's "WORTHY" system; it seems to have some as of yet unknown criteria by which it decides if a player is 'worthy' of experiencing the Eternal Fort or not. Due to this worthiness system, and the already obscene rarity of even finding a copy that may contain it, no data on the anomaly's appearance and in-game effects are known.
Anomalous Effects
The Eternal Fort appears to invoke some form of mild paranoia in anyone who experiences it. Out of the few players that have claimed to have seen the Fort, most chose to remain almost silent, declining to give any detailed information on what the Eternal Fort is.
There also may be some form of memory-loss effects tied to the Eternal Fort, as to date anyone that the game deems "unworthy" and has attempted to view the Eternal Fort first-hand (usually by observing a 'worthy' player) all memory of the game seems to dissappear from memory.
Purpose
The real purpose of such an anomaly is almost entirely impossible to determine with the little information available. However, several theories have been proposed as to what the Fort really is and was.
The most common theory to what the Fort is, in terms of a literal geographic descriptor, is Bowser's Castle itself. Some (unconfirmed) sources on-line refer to the area as "Bowser in the Eternal Fort", which is the basis for this theory. It could also be any variation of a Bad Ending castle, such as the Sunken Castle or a very large Bowser's Domain.
A blurry image of a castle-like structure.
Secrets
Almost everyone who claims to have seen the Fort vaguely reference some form of 'Secret' or 'Truth' that they somehow learned whilst experiencing the anomaly. All attempts to request elaboration have failed thusfar, leading the nature of this Secret to be left unknown. This is likely the reason that players are so paranoid to even mention the Fort's existence, assuming this Secret is of a scope larger than expected.
ETERNAL FORT (REAL) - SUPER MARIO 64 SOUNDTRACK
The song in question.
The secret is likely related to the A.I itself; given it's nature as a highly secretive anomaly that the A.I seems to have a 'filtering' process for. This is mere speculation however, and this supposed 'Secret' could be very well unrelated to Super Mario 64 as a whole.
Music Track
A song claiming to be the real song of the Eternal Fort was uploaded to YouTube by an account named "The Nintendissident." While it is impossible to definitively prove the legitimacy of this track, it is commonly believed to be the real track of the anomaly, or atleast somehow related to it. The account has the channel description of "I AM HERE TO DISSEMINATE THE TRUTH ABOUT MARIO 64 BETA", which seems to tie-in to it's posting of the Eternal Fort track.
Images
Few and far between, images claiming to be of or related to the Eternal Fort have surfaced online in varying locations. While the legitimacy of these images is near impossible to confirm, the nature of these images seems to be in-line with what is presently known about the anomaly.
Context unknown. The un-textured model in the background may be the Eternal Fort or somehow related to it.
