The popularity of RPGs like Wizardry and Dragon Quest had a huge effect on the Japanese video game marketplace. This was visibly seen in many Famicom games at the time, like Zelda II and Castlevania II, which adopted RPG elements not found in their previous games. While most would agree that RPG aspects are better left to console games, which are generally longer and therefore more suitable to home play, there were still a number of arcade games that tried to integrate some of these elements, like featuring character classes or allowing you to obtain money to buy more equipment. The earliest and most successful of these were Westone's Wonder Boy in Monster Land, Namco's Valkyrie no Densetsu, and Taito's Cadash. Data East also jumped on the bandwagon in 1990 with Dark Seal, also known as Gate of Doom.
Dark Seal casts you as one of four characters, commanded by the King of Etrulia, to save the realm from the evil Volov and his right hand man, the Black Knight. Taking place in a medieval fantasy world obviously inspired by Dungeons and Dragons (even more so than the earlier similar games), each of the players fill a familiar role-playing archetype, illustrated via character sheets in the introduction.
Carl F. Graystone is the knight, slow but wielding a powerful morning star, which is swung around in a circle. Freya Edirne is the wizard, subverting expectations by not being a bearded old guy but rather a woman who dresses in Egyptian-style garb. She wields a "flame pillar", which shoots blazes of fire along the ground.
Riger Hawk is a bard, which one would think would be useless in an action game, but he holds his own thanks to a weapon called an "elastic spetum", which is a sort of multi-headed spear that fires out shadow duplicates of itself. As a bonus, he's also immune to poison. Finally, there's Kirikaze the ninja, who attacks with shurikens.
The levels are presented with an isometric perspective, though your character can move in all eight directions. There are treasure chests everywhere, which grant assorted items. Most are just for score, but some can temporarily improve your speed, strength, or defense. There's also a magic meter, which slowly grows as you dispose of enemies. All of the characters can actually wield magic, not just the wizard, though the spells they're able to use are different. These are indicated by the book above the magic meter, which flips through the spell pages automatically, so you need to wait until it brings up the magic you want to use.
Once fully charged, you can press the secondary button to cast it, which will temporarily change your form and give yourself new attacks. You can turn yourself into a ball of flame to set things on fire, or a tornado to toss bad guys into the sky. Less typical magic includes turning yourself into a Medusa head to change enemies into a stone; a giant rat, which is stronger than you'd think considering you also control a small army of rodent companions; a boulder, which struggles with its own weight when it tries to move but can cause damaging earthquakes by jumping; and a treasure chest, which will spit out a handful of bonus items. However, despite changing form, you're still vulnerable to enemy attacks, so they all feel underpowered compared to how much you need to charge up to activate them.
Despite all of these magic spells, equippable items, and character selections, the core of Dark Seal is fairly uncomplicated, rarely going beyond "walk forward and smash stuff". It actually feels like an evolutionary mid-way point between the simple arcade action of Gauntlet and the slightly more elaborate hack-and-slash dungeon crawling of Diablo.
Working your way through the levels isn't too hard at the beginning, as long as you're careful, but the enemy numbers and strength can be overwhelming near the end. Plus, the bosses are the worst parts of the game. They're huge, with attacks that are extremely difficult to avoid, and they take tons and tons of damage, which is especially a problem if you're playing solo. The penultimate boss tosses out a huge number of status effects, including confusion, petrification, paralysis, and even turning you into a pig. It's neat to see status effects in an action-arcade game, but it sure is massively frustrating. They do look cool, though - most of them are varying types of dragons, and they die in satisfying fashions - in the first stage, the boss's head falls right off, while a later foe crumbles into pieces.
Outside of the dragons, the visuals are generally unremarkable. The sound design, however, is great. The soundtrack ranks right up next to similarly styled fantasy action games like Golden Axe and Rastan, and the numerous digitized sound clips of the warriors screaming all kinds of stuff are gleefully silly.
While nearly all of the arcade games that tried to implement RPG elements had some type of balance issues, Dark Seal is probably the weakest, and even its setting seems unremarkable considering the actual Dungeons & Dragons beat-em-up, which was released a few years later by Capcom. At least things improved a little bit in the sequel.
Two years after the original, Data East followed up Dark Seal with a sequel, known as Dark Seal II in Japan, and Wizard Fire elsewhere, disavowing any relationship to any previous games. (It's easy to assume that the first game was not very popular abroad.) Within those two years though, the visuals have massively improved, a benefit of moving to more powerful hardware. (Even back in 1990, Dark Seal looked a little dated for an arcade game.)
The game fundamentally works the same. There are five characters this time - the ninja is gone, with two new characters, an axe throwing dwarf named Jade Greataxe and a female sword wielding elf named Eminna Jozestore. There are some subtle tweaks in how certain characters play. For example, with the knight and the wizard, you can charge up your weapon strength by not attacking for about a second, which means it's generally better to not button mash. The elf and the bard are the opposite, though, as button mashing will trigger a special multi-hit attack. Otherwise, the bonus stat items and the magic spells are basically the same.
Most of the first game's flaws have not been addressed either. The early bosses are a little quicker to take down, and you can now cast magic during them (though since you generally can't build up magic power when fighting bosses, it's not all that useful), but some of the later foes are gigantic pains. The most egregious one is a battle against two golems, which can only be damaged by hitting their heads, and seem to take a few hundred whacks before they finally go down.
In fact, some things are even more irritating. Status effects, particularly confusion, are much more prevalent this time around, and certain levels have a proliferation of tiny enemies that are very difficult to see. Plus, the first game offered a number of lives per credits. Dark Seal II only gives you one, and it goes quickly, though it's nice enough to bestow some bonus items upon you when you continue.
And yet, Dark Seal II ends up being a more enjoyable experience simply because it looks much better and has a much greater personality. There wasn't much of a story in the first game, just some quick cinemas of the king ordering you around. Here, each level is prefaced with anime-style cutscenes, fully voiced in either English or Japanese. The artwork is pretty good, but both the voice acting and the writing is comically bad, often on the level of a Saturday morning cartoon.
At the outset, the party members discover a ruined town, and suspect that Volov, the penultimate foe from the previous game, may be the culprit. "I heard rumors that Volov may still be nearby", proclaims the dwarf. Then they turn around and see Volov and his dragon, who cackles, "I'm closer than that, fools! I'm here!" before launching a surprise attack.
At the end of the third stage, the gang encounters a polluted river. "Curse it! Poisoned water!", the bard exclaims. "I'll smash it to bits!" daftly proclaims the knight, who seems to be unclear of what exactly the problem is. Before the fourth stage, your party notices that the castle they need to infiltrate is flying in the sky. "So do we grow wings?" suggests Jade, who isn't entirely sure if he's being sarcastic. "No, Jade. We'll use MAGIC", proclaims the wizard, a solution that sounds like it came from one of the lesser Disney princesses.
During the game the visuals are superior over the first game by several orders of magnitude. The original Dark Seal had a very dark fantasy-style, with a dark palette typical of many late 80s Data East games, while the sequel trades it for a much more colorful anime aesthetic.
Along with the large characters and isometric perspective, Dark Seal II ends up resembling Taito's similarly-themed brawler Dungeon Magic / Light Bringer, which was released a few years later in the arcades. The style is also similar to Data East's horror beat-em-up Night Slashers, even though otherwise it's nowhere near that level of quality. What it ultimately adds up to is a game that's a fair bit of goofy fun, even though it's technically not all that good.
While the original Dark Seal wallowed in obscurity, the sequel was included on the Data East Arcade Classics for the Wii, though it's just a straight emulation, along with some jagged display issues that affects every other game on the compilation.