This little post is for those readers who aren’t familiar with the Final Fantasy series and may need a little more insight to some of the lore behind its multiverse.
Up until Final Fantasy 10 the series of games did not feature direct sequels. Though FF4 featured a mobile phone sequel entitled The After Years, game consoles did not see a direct sequel to an FF game until FF10-2. The series of games, however, share much in common lore, though some games may be missing certain elements.
Crystals: The original Final Fantasy (I will refer to as Origins, or FFO) started with the four warriors of light, each carrying a dim crystal orb. From FFO to FF5 the series included some reference to or have a storyline directly tied to these crystals. Typically they are elemental crystals, with at least four representing one of the four elements (earth, wind, water and fire). Some games include additional crystals like dark crystals. Other games in the series did not have direct references to the crystals, but included some type of crystal that was important to the game (FF6 had magicite, FF7 had materia).
Jobs: FF Origins began with four characters under the players control. Those four characters could be assigned one of several different classes (Fighter, Thief, White Mage, Black Mage, Red Mage or Monk). At some point in the game your characters would gain enough strength to change their class to an improved version (Knight, Ninja, White Wizard, Black Wizard, Red Wizard and Master). In later games these classes would be called Jobs and would become a central focus of gameplay. Some games would allow you to change your Job by changing out items (crystals or weapons), while other games would not allow you to change the Job of the characters (FF4, FF6). Even though you could not change Jobs in these games, they were instantly recognizable. Some of the most popular and long-running jobs are: Warrior, Ninja, Summoner, Black Mage, White Mage, Red Mage, Samurai, Gunner, Beast Master, Dragoon, Dark Knight, Paladin, Thief, Blue Mage, Archer and Monk.
Magic: Essential to any fantasy type game is magic and the FF series does not let down. Each game in the series has some form of spell casting or another and along the entire series certain spells are common, often with different levels of power. For example the spell for an ice attack is commonly called Blizzard, with more powerful spells named Blizzara, Blizzaga and Blizzaja. The weird naming convention has to do with the Japanese language (ra, ga and ja have different meanings on the ends of words, I think). There are different spells used for attacking an enemy or causing negative status effects (called ‘debuffing’) as well as spells for healing party members or giving them beneficial status effects (called ‘buffing’ or ‘buffs’). Spells common in the series are Blizzard, Fire, Thunder, Quake, Bio, Sleep, Poison, Confuse, Cure, Protect, Shell, Wall, Ultima, Flare, Holy, Dia and Blind.
Chocobos: The workhorses of the Final Fantasy multiverse, Chocobos (pronounced cho-ko-bo) are giant yellow birds, large enough to pull carriages or even be equipped with a saddle for riding. Their presence has been felt in every game one way or another, and they have been featured as Jobs (Chocobo Knight), monsters (Wild Chocobo) and even as summoned monsters!
Moogles: Another staple of the FF series moogles are unique to the FF world. Often times they are flippant and cannot be taken seriously, but can be vicious warriors and powerful spell casters. Some games have had them as playable characters, but mostly they just play part in the stories. In some games normal people cant even see them.
Summons: The Summoner is a staple job in the FF series, and their main ability is to magically summon otherworldy beings that will either deliver a powerful attack or fight in their stead. Some games forgo the summoner job and allow you to summon these beings through other means (materia, magicite, equipped GF). They are sometimes referred to differently in different games. FF8 calls them Guardian Forces, FF11 uses the term Avatars, FF13 refers to them as Eidolons. Though often summoned to assist the main characters, they can sometimes be enemies as well. FF14 uses many of the summoned monsters from previous games as antagonists to the players character, and some of the games in the series require you to defeat the summoned monster before they can be summoned. The games initial use of summoned monsters was to deliver a single attack against enemies (FF3-FF9), but FF10, 11 and 12 allowed players to summon one of these beings to fight in their stead or alongside them. Summoned beings include Shiva (ice), Ifrit (fire), Ramuh (lightning), Titan (earth), Bahamut (king of dragons), Odin (blade master), Leviathan (water), Diablos (dark) and Garuda (wind).
Cid: Every FF game contains at least one character named Cid. Not always a playable character, Cid is often an older, wiser male character who aids the party in some way.
Biggs and Wedge: So, apparently someone in the FF development office is a fan of Star Wars because Biggs and Wedge (referencing Biggs Darklighter and Wedge Antilles of Episode 4 fame) are a recurring pair in the game series.
Weapons: Certain weapons have recurring roles in the series. Ultima, Ragnarok, Masamune, Mythril weapons, Icebrand, Diamond weapons, Excalibur and Excalipoor are all weapons that appear in multiple games.
Gil: Earlier games in the series used the common ‘Gold’ for a monetary denomination, but later games in the series (I think starting with FF7) started using ‘Gil’ (pronounced however you want: GIL or JIL). It now seems to be the default monetary denomination in all FF games.
The Prelude: One of the most beautiful melodies I have ever heard, the musical piece known as ‘The Prelude’ or ‘The Crystal Theme’ is played in some form in every game in the series. What started as a few simple notes, rising and falling, has turned into one of the most iconic tunes in all of gaming. Do yourself a favor and listen to both versions linked here, and then go to YouTube and listen to the different versions from each game. The songs evolution is great.
I’m sure there are many more elements I could go over, but these seem to be the most recurring and most notable of the series. I would advise looking at the Final Fantasy Wiki if you have further interest in information.