As HBO’s juggernaut, Game of Thrones, returns for its final season, fans are catching up on all of the theories out there pertaining to the end game. One of those theories is called the “Great Other.” So, what does this theory entail?

According to Refinery 29, the Great Other is the opposing force to the Lord of Light in that religious faith. However, this deity has only been mentioned in the books that the TV series is based on — so far. This means that the Great Other may not come into play in the final season. However, many fans of the books believe that it will, considering it is considered to be the other half of the Lord of Light faith, also known as the R’hllor religion.

The R’hllor faith is considered to be dualistic in style. The Lord of Light is good — even if it doesn’t look that way under the guidance of Melisandre (Carice van Houten). By comparison, the Great Other is considered to be filled with evil. While this deity hasn’t been revealed in the television series, there is some sort of reference to it every time that Melisandre refers to the fact that the night is dark and full of terrors. The Great Other is also referred to as the God of Night and Terror.

Why Is The Great Other Important?

Followers of the R’hllor faith believe that the struggle between good (the Lord of Light) and bad (the Great Other) is eternal. They also believe that there is a human element, Azor Ahai, who is resurrected whenever required on behalf of the Lord of Light.

Azor Ahai led the very first battle against the White Walkers, according to Game of Thrones history. And, as a result of this, it is believed that Azor Ahai — also known as the Prince Who Was Promised — will return soon to help with the current threat from beyond the Wall.

Already, Game of Thrones viewers have heard of the Prince Who Was Promised. Melisandre initially thought that Stannis Baratheon (Stephen Dillane) was this promised prince. Then, when he died, Jon Snow filled that spot. There are other theories as well. Considering it has already been noted that the translation from Valyrian could mean prince or princess, there is the suggestion that Daenerys Targaryen (Emilia Clarke) could also be the promised one.

While there has been a lot of discussion about the Lord of Light’s human element in Azor Ahai, very little has been said regarding the human counterpart for the Great Other. However, some fans suggest that Bran (Isaac Hempstead Wright) is the Great Other’s counterpart as the Three-Eyed Raven.

In addition, there is the suggestion that the Great Other is actually the leader of the White Walkers, also known as the Others in the book series that Game of Thrones is based on. This would mean that the Great Other’s champion could already be in Westeros in the form of the Night King (Vladimir Furdik).

Of course, fans will have to tune into the remaining episodes of HBO’s Game of Thrones to find out if the Great Other makes an appearance in the final season and what the outcome will be.

Season 2 of Game of Thrones returns to HBO with Episode 2 on Sunday, April 21, at 9 p.m. ET.