I was a little unsure of this game going in, but it ended up becoming one of my favorite games on the PS2.
The core of the gameplay is more or less a Diablo-style game, where you control both (although only one at a time) a melee-focused and a magic-focused hero, as well as getting two NPC companions to follow you around. The AI aren't brilliant, but they always seemed competent enough, and are a good augmentation of your own hero's shortcomings (i.e., big melee guys usually go with the magic-hero, and ranged/magic/healers usually go with the melee-hero). The melee-user Toma is a great blast to play as. His two combat options are single-handed weapons, or two-handed ones, where single-handed allows you to use a shield as well for extra defense. Personally, I pretty much always used 2-handed weapons, because I found that the amount of max HP you have usually is much more important than your defense, because the stronger monsters can usually just one-shot you (if you're in an area too strong for you), so I just tried to use the two-handed weapons' much greater attack power to kill them before they'd kill me.
Cyrille on the other hand seems kinda crap at first, but I'd say around the 3rd or 4th chapter she became my preferred member to use in outside exploration (more on that later). Her two options are either tomes which allow her to use specific magics within them, or crossbows. Her crossbows are one-handed just like her tomes however, so unlike Toma she can always use a shield. Personally, I only used crossbows when I was completely out of mana, and there really isn't a good way to replenish mana out in the field. Once you level up the strength of a specific magic element though, she becomes a monster: You can basically just walk towards stuff and it dies (although it's not quite that simple, in practice).
Another reason I loved this game is because of the fact that it has not only great loot, but great loot customization. Along with the piles of gold you'll find to add to your heroes' shared gold-pool, which allow you to buy equipment from the shop, have the shop identify your items, or get base-upgrades for equipment at the blacksmith, there's another currency of mythril. Mythril is used to upgrade "Power Arts," which basically serves as a way to beef up specific base-stats in a way you want to prioritize most, although you do have to find obelisks out in the game world to unlock more powerful power arts to tech into, thus exploration of EVERYWHERE is highly encouraged. In addition, unlike with gold, all of the mythril you find gets added to BOTH heroes total mythril counts, meaning it's much easier to upgrade them both just as you want, and you don't need to prioritize who picks up how much mythril. You can also turn unwanted items into either gold OR mythril, letting you prioritize different aspects of upgrading as you see fit.
Lastly on customization, the game has tons of optional areas, ranging from glowy (not power art) obelisks which you can break to unleash powerful monsters, to "Ancient Arenas" which test your mettle against many monsters, to get Secret Scrolls to unlock "Secret Arts," one of which at a time can be added to a piece of armor as a fairly significant passive-boost, with weapons, shields, hats, and armor each having their own respective secret arts to be used with. Honestly, later in the game, it comes down to the opportunity cost of which one you want to use compared to the others, because they're usually so good. The best part is, you have a limitless home-teleport option you can use almost whenever you want, so you can jump home whenever to swap up your equipment, power arts, secret arts, etc. whenever the fight isn't going your way, or if you just wanna dump off some items.
ANYWAY, customization aside, the Diablo-style gameplay is divided into two parts (kinda), "offensive" exploring, and defensive missions. You get a main base very quickly in the game, and everyone else in the world wants your cool base, so they'll try to destroy your power supply. Every hour or so, a random event will occur (occasionally they're scripted though) and you'll be brought away from the action of the guy you have out on the offensive back to the home base, where the guy you aren't using will get a chance to bash some heads in and level up. I usually left Toma home for these, because as they usually involve killing some big boss or artillery piece, his limitless powerful swings were much more practical than Cyrille who will usually run out of mana blasting other fools before that goal can be achieved.
The story starts off fairly slow and off-putting, with the voice acting being pretty hit or miss and the initial reason for your quest not being very compelling. I really got attached to it around a third of the way through the game though. The writing on the main heroes and your companions is okay, but the writing of the villains (or at least their character arcs) is excellent, in terms of being fairly realistic in their motives and actions, and they interact with your characters consistently.
As far as things I didn't like, I guess the inventory management system was a bit annoying at times. Your characters have their own individual inventories, so you need to go back to home base to switch anything between them via the storage system, but seeing as how easy returning to base is, and how you need to get virtually any piece of equipment you find identified before you can use it, I never really found it a problem, so much as a minor inconvenience, as loading times are pretty short.
TLDR: A great Diablo-style game on PS2. I honestly enjoyed it far more than Diablo 3, even though I played this game far more, and did everything you possibly could in it. This is hands down one of my favorite actions games ever, let alone on PS2. (It would be pushed to god-tier if it had any multiplayer, but sadly it does not. I have no friends to local-Diablo with at the moment anyhow though, so that didn't affect my experience.)
The core of the gameplay is more or less a Diablo-style game, where you control both (although only one at a time) a melee-focused and a magic-focused hero, as well as getting two NPC companions to follow you around. The AI aren't brilliant, but they always seemed competent enough, and are a good augmentation of your own hero's shortcomings (i.e., big melee guys usually go with the magic-hero, and ranged/magic/healers usually go with the melee-hero). The melee-user Toma is a great blast to play as. His two combat options are single-handed weapons, or two-handed ones, where single-handed allows you to use a shield as well for extra defense. Personally, I pretty much always used 2-handed weapons, because I found that the amount of max HP you have usually is much more important than your defense, because the stronger monsters can usually just one-shot you (if you're in an area too strong for you), so I just tried to use the two-handed weapons' much greater attack power to kill them before they'd kill me.
Cyrille on the other hand seems kinda crap at first, but I'd say around the 3rd or 4th chapter she became my preferred member to use in outside exploration (more on that later). Her two options are either tomes which allow her to use specific magics within them, or crossbows. Her crossbows are one-handed just like her tomes however, so unlike Toma she can always use a shield. Personally, I only used crossbows when I was completely out of mana, and there really isn't a good way to replenish mana out in the field. Once you level up the strength of a specific magic element though, she becomes a monster: You can basically just walk towards stuff and it dies (although it's not quite that simple, in practice).
Another reason I loved this game is because of the fact that it has not only great loot, but great loot customization. Along with the piles of gold you'll find to add to your heroes' shared gold-pool, which allow you to buy equipment from the shop, have the shop identify your items, or get base-upgrades for equipment at the blacksmith, there's another currency of mythril. Mythril is used to upgrade "Power Arts," which basically serves as a way to beef up specific base-stats in a way you want to prioritize most, although you do have to find obelisks out in the game world to unlock more powerful power arts to tech into, thus exploration of EVERYWHERE is highly encouraged. In addition, unlike with gold, all of the mythril you find gets added to BOTH heroes total mythril counts, meaning it's much easier to upgrade them both just as you want, and you don't need to prioritize who picks up how much mythril. You can also turn unwanted items into either gold OR mythril, letting you prioritize different aspects of upgrading as you see fit.
Lastly on customization, the game has tons of optional areas, ranging from glowy (not power art) obelisks which you can break to unleash powerful monsters, to "Ancient Arenas" which test your mettle against many monsters, to get Secret Scrolls to unlock "Secret Arts," one of which at a time can be added to a piece of armor as a fairly significant passive-boost, with weapons, shields, hats, and armor each having their own respective secret arts to be used with. Honestly, later in the game, it comes down to the opportunity cost of which one you want to use compared to the others, because they're usually so good. The best part is, you have a limitless home-teleport option you can use almost whenever you want, so you can jump home whenever to swap up your equipment, power arts, secret arts, etc. whenever the fight isn't going your way, or if you just wanna dump off some items.
ANYWAY, customization aside, the Diablo-style gameplay is divided into two parts (kinda), "offensive" exploring, and defensive missions. You get a main base very quickly in the game, and everyone else in the world wants your cool base, so they'll try to destroy your power supply. Every hour or so, a random event will occur (occasionally they're scripted though) and you'll be brought away from the action of the guy you have out on the offensive back to the home base, where the guy you aren't using will get a chance to bash some heads in and level up. I usually left Toma home for these, because as they usually involve killing some big boss or artillery piece, his limitless powerful swings were much more practical than Cyrille who will usually run out of mana blasting other fools before that goal can be achieved.
The story starts off fairly slow and off-putting, with the voice acting being pretty hit or miss and the initial reason for your quest not being very compelling. I really got attached to it around a third of the way through the game though. The writing on the main heroes and your companions is okay, but the writing of the villains (or at least their character arcs) is excellent, in terms of being fairly realistic in their motives and actions, and they interact with your characters consistently.
As far as things I didn't like, I guess the inventory management system was a bit annoying at times. Your characters have their own individual inventories, so you need to go back to home base to switch anything between them via the storage system, but seeing as how easy returning to base is, and how you need to get virtually any piece of equipment you find identified before you can use it, I never really found it a problem, so much as a minor inconvenience, as loading times are pretty short.
TLDR: A great Diablo-style game on PS2. I honestly enjoyed it far more than Diablo 3, even though I played this game far more, and did everything you possibly could in it. This is hands down one of my favorite actions games ever, let alone on PS2. (It would be pushed to god-tier if it had any multiplayer, but sadly it does not. I have no friends to local-Diablo with at the moment anyhow though, so that didn't affect my experience.)