DQ's soundtrack. The soundtrack credits the music with Hitoshi Sakimoto, and there were even rumours that Yasunori Mitsuda had some involvement here. Even by themselves, they are both pretty good at often serene and atmospheric music. (And DQ's really represents a society on the brink of crumbling, just barely struggling to stay alive, let alone make progress)
Yuna in IV has quite a few of these surrounding him. There is a portion of the base that believes he created Myria and set the entire series into motion. This theory stems from the fact that he pulls a Karma Houdini at the end of the game and announces that he wants to create more gods. Of course, this assumes that the game is a prequel to the others, which has not been confirmed. Now that the manga is concluded, his continued existence — along with the survival of Fou-lu — has a few people thinking that he may be coming back as the Big Bad of a sequel or side-story.
According to the Creative Closing Credits in II, the elder of Dologany is named "Ryu Rider"...could he be I's Ryu?
Overly-literal translation of "Dragon Leader"?
It's likely to be this, since the original translation of the game was one of the worst cases of "Blind Idiot" Translation.
Fanon: The current Ryu and Nina are the reincarnations of the Ryu and Nina from the previous games and they are soulmates.
Due to the fact that the exact position of IV has never been established timeline-wise, there are at least two fanon interpretations as to where the game fits (not counting Alternate Universe explanations). The most popular "Fanon Timeline" places IV as a Non-Linear Sequel (specifically as a sequel in the distant past) to I-III, with an entire constellation of fanon related to this interpretation, specifically involving where Myria came from.
Capcom indulges in a big one by having not taken advantage of the GBA re-releases in order to fix the translation discrepancies (specially in II) and not making use of the chance to expand on some Plot Holes (Patty's whereabout probably being the biggest).
Moral Event Horizon: for Harabuku: Murdering Tiga and Claris, causing the death of Daisy, ruining Ryu's life, torturing Ganer for ten years in a secret facility beneath the Evrai Church, sacrificing innocent souls to the Big Bad...the list goes on.
Whenever Yuna makes an appearance, expect him to do something horrifically evil. Mutating Elina into a disfigured Endless that can be used as a sacrifice for the Carronade is probably his worst deed, and the fact that her boyfriend Cray has to mercy-kill her afterwards only makes it worse. Even more disgustingly, Elina came to visit them on a goodwill mission. He also turns Fou-lu's love interest Mami into a Sacrificial Lamb for the same cannon, which convinces him that Humans Are the Real Monsters and that they deserve to die.
When Captain Rasso mercilessly slaughters the summoners of Chek. Just to make it worse the summoners in question looks like children and it's made even worse in the manga since they acted very heartwarming towards a doubting Ryu.
Portmanteau Couple Name: RyuNina in the series in general. Most other known portmanteaus tend to be restricted to Japan, some have made it to other countries, though.
In IV, FouMami (for the het pairing), FouRyu (for the selfcest pairing), and in Japan SciAsu (Scias x Ursula/Asura) also exists. FouMami, in fact, is probably the most well known portmanteau naming in the Breath of Fire IV fandom.
In DQ, RyuBo (Ryu x Bosch) is a known portmanteau in Japan.
In II, RyuKatt is a known portmanteau for the obvious pairing. Interestingly, in Japan there is not a RyuRin (Ryu x Rinpoo) equivalent.
II in particular also has a lot of portmanteau namings not related to couple pairings, but rather from fusion forms with other members of your party.
Sequelitis: Breath of Fire 6 is widely agreed to be this, being a generic mobile game that has little in common with the series. Capcom seems to agree as the server only lasted a year before being shut down.
Tear Jerker: Each game is usually good for about two or three.
I: Alan and Cerl's deaths (if they actually died), being forced to fight against and kill your sister.
II: The death of Rand's mother, the death of Tiga and Claris, the death of Ray, and the death of Ryu's mother.
Also Mina's becoming a great bird, especially with the music.
III: Teepo's death, especially his dying words. And Rei's response to it.
IV: Elina's death, period. Mami's (Fou-Lu's girl) death also counts.
And from Volume V of the manga, Fou-lu breaking down when confronted by Ryu over how Mami was the counterexample to Humans Are the Real Monsters. Fou-lu is definitely not the Iron Woobie here...
Ershin: "Was that... an appropriate time to laugh?"
Jade/Judas's death in The Dragon Warrior, along his lover Sara.
That One Boss: Wildcat the chef from II. Before you fight against him, you have to exchange all of your kickass equipment for a knife, a napkin, and a plate (as a shield); and also attract enemies by rubbing salt and pepper on your bodies. While you're equipped with the game's equivalent of heart, Chef Wildcat's chopping and dicing up your party with moves that can be close to an instant-kill if your HP are low enough. Try to sneak into his office with your weapons, and the bouncer (or "maître d'") will be more than happy to stomp a mudhole in you.
The bouncers are actually somewhat manageable, but unfortunately, it seems you can't get out of losing all your items and sacrificing 1/4 of your HP.
It turns From Bad to Worse: if you ignore the last sign that tells you how you like your meat cooked and get to the oven, the oven will fry your entire party and reduce all their HP to One (which is the same as choosing your meat "well-done" if you had read it), which means that you're dead meat if you don't heal all your party's HP pretty quick!
If one is willing to go Nintendo Hard, it is possible to get the ChopChop attack (a very useful physical attack best suited for Nina) as a reward from this, but it requires the player to take out Wildcat MUCH sooner than the storyline requires you to and obey the signs except for being allowed to choose rare on the last.
Gremlin in I as well. As soon as he Turns Red he uses his best attack every turn and has about two or three times his HP bar left.
Horn Toad in I has a nasty habit of using earthquake jumping moves a lot after he Turns Red.
Algernon in II. It has two companions, one heals roughly 100HP each turn, another does an AOE attack, in addition to Algernon's AOE attack. Among other things.
Barubary/Barbaroi. Definitely one of the toughest opponents in the second game.
That One Level: The Desert of Death from III, a Guide Dang It! made even more so by a mistranslation that sends you in completely the wrong direction, made even scrappier by the fact a rather silly Insurmountable Waist-Height Fencenote The only thing stopping you from going straight to the final dungeon after getting the portal network working again is the fact that nobody in your party has the guts to hop down from a 6-foot-tall crate. is the only thing preventing you from skipping it.note And it had the simplest solution: turn 1 degree to the right; from that direction, it's literally a straight path.
It has a counterpart in IV that isn't much better. Seriously, who at Capcom could have thought this was a good idea?
The crystal-path maze in Mote/Sigmund's nightmare.
Also from I, the tower in Mogu's dream world; there are certain tiles that turn all of the walls invisible, making it very easy to get lost if you don't know exactly where you're going.
Similarly, there's also the Memory Tower in II, due to the fact that you can only see a few spaces in front of you.
and IV