In 2004, Raven Software surprised a lot of people with X-Men Legends, an action RPG focusing on the exploits of Marvel's mutant superheroes. The Diablo-style gameplay was a significant departure for Raven, a developer best known for its extensive work on first-person shooters. Perhaps more surprising was the game's success in introducing action RPG conventions to the world of superheroes, a fairly novel combination at the time. It proved to be a winning formula, one that Raven further refined with last year's X-Men Legends II: Rise of Apocalypse. Not content with the localized struggles of the X-Men, the concept has been blown out to an intergalactic, interdimensional scale with Marvel: Ultimate Alliance. With well over 20 unique playable heroes, a massive campaign that features a wide variety of well-known Marvel Universe villains, supporting characters, and locations, as well as plenty of hidden extras, it's the biggest piece of Marvel fan service seen in a video game. It also builds upon a lot of the gameplay systems established in the X-Men Legends games, making for an experience that's deeper, longer-lasting, and generally more satisfying. As it did with X-Men Legends II: Rise of Apocalypse, Vicarious Visions somehow crams nearly all of the content found in the console versions of Marvel: Ultimate Alliance into the PSP.

he stars of the world's greatest comics join forces in Marvel: Ultimate Alliance.

Ominous things are afoot right from the start in Marvel: Ultimate Alliance. Dr. Doom has brought together a coalition of supervillains under the Masters of Evil name, whose first act is to attack a S.H.I.E.L.D. helicarrier. An opposing coalition of superheroes quickly comes to the aid of S.H.I.E.L.D. director Nick Fury, who takes command of the situation and coordinates the superheroes as they continue to track Doom and his minions across the universe and into different dimensions. The sheer quantity of Marvel supervillains you'll face on your quest to defeat Dr. Doom is genuinely staggering. Heavy hitters like Ultron, the Mandarin, Mephisto, Loki, and Galactus all play major roles, but there's still room for lower-profile villains like M.O.D.O.K., Fin Fang Foom, Arcade, Grey Gargoyle, Blackheart, Super Skrull, and literally dozens of others. There are a couple of truly excellent twists and turns, and the story does a good job of concealing the true nature of Dr. Doom's plans until just the right moment. Some of the finer points, such as the excess of long-winded expository speeches in between levels, don't stand up to close scrutiny so well, but the narrative is successful in keeping the game moving at a fast clip.

Your starting lineup in Marvel: Ultimate Alliance consists of Captain America, Thor, Spider-Man, and Wolverine, but after a few levels playing with these heroes, you're given the option to create your own custom team. At first you'll have about 18 different heroes to choose from, and they represent a good cross-section of high-profile heroes and more obscure fan favorites. Old-schoolers like the Fantastic Four, Iron Man, and several X-Men are there, as are a number of heroes who are likely unknown to those who don't keep up with comics, such as Moon Knight, Luke Cage, Spider-Woman, and Deadpool. As you progress you'll run into other heroes such as Blade, Dr. Strange, Ghost Rider, and the Silver Surfer, who will in turn join the cause. The PSP version features a slightly different lineup, with Colossus and Moon Knight being replaced by Hawkeye, Captain Marvel, and Ronin.

Part of the fun of Marvel: Ultimate Alliance is the sheer variety of places the game takes you. While the X-Men Legends games seemed stuck mostly in dungeonlike corridors and sewers and such, here you'll visit some of the most spectacular and mythical locations in the Marvel Universe, including Mephisto's Realm, Asgard, Mandarin's palace, the Skrull homeworld, and, finally, Dr. Doom's sinister Latverian castle. Many of the environments really do look as if they came straight out of a comic book. As nice as Marvel: Ultimate Alliance on the PSP can look, the zoomed-out overhead camera angle can make the action seem indistinct. Not being able to see the enemies you're supposed to be fighting can be most frustrating. The sound design is also a little uneven, with some overly chatty characters and environmental sound loops, but it more than makes up for this with a soundtrack that's just fantastic, capably shifting gears to keep up with the game's near-constant, dramatic scenery changes.

Character customization runs deep, though you can choose to automate it if it's too much for you.

The basics of the gameplay should be perfectly familiar by now to fans of hack-and-slash dungeon crawlers like Diablo, Baldur's Gate: Dark Alliance, or Raven's own X-Men Legends games. Commanding a group of four superheroes, you'll fight your way through swarms of enemies, becoming more powerful and gaining new abilities and the occasional piece of gear along the way. From the get-go, everyone can perform a handful of straight-up melee combos. There are a few details that give the basic combat some depth beyond simple button mashing, such as the ability to disarm enemies and grapple with them and enemies that are only susceptible to specific attacks. Each hero has a unique set of special powers, and these special powers, along with, for example, the ability of flight when appropriate, play a big part in giving each hero a unique feel. As different as the abilities can look and feel, most can be easily slotted into a handful of categories. There are melee attacks, radial attacks, projectile attacks, beam attacks, individual and team boosts, and high-powered "xtreme" attacks that you can only trigger after your usually slow-filling momentum meter reaches capacity. Save for the Silver Surfer, who seems stymied by the terranean nature of the gameplay, the heroes feel quite comparable to their ink-and-paper counterparts.

Though you have little control over how your heroes' basic stats (like health and energy) increase, with each new level you're given skill points that you can put toward special powers. Each hero has eight or more special powers in an arsenal, though many of them are inaccessible until you reach certain experience plateaus. You can also use cold, hard cash that you pick up by beating enemies and smashing crates to purchase points, though they start off pricey and become exponentially more so as you progress. Each hero also has three alternate costumes that you can unlock, which not only can drastically affect the hero's appearance, but also come with a unique set of bonuses that you can pay to increase. Defeating significant villains and finding special treasure chests will usually net you a piece of performance-enhancing equipment. Usually any hero can use any gear you happen upon, though it never shows up on their person, and there are also lots of rare pieces of gear that only specific heroes can use.