Overall, Monster Sanctuary is an interesting title with a fairly basic overview that steadily gets more complex the more you look under the hood. At its core, it's a monster catching game with some platforming elements (side-scrolling, reminds me of a more cartoony Symphony of the Night or Valkyrie Profile in terms of controls) as there's no real way to 'run' for more distance (although the walking speed is perfectly acceptable) but you do eventually unlock a double-jump to access other areas.
But where it starts to get interesting are the monsters themselves. Each monster has innate strengths and weaknesses to different types of damage (physical, fire, ice, nature, wind, poison, etc. There are quite a few) similar to Pokemon, but the S/W are dependent upon the monster.
Beyond that, each monster, as it levels, has 3-4 skill trees that you put points into in order to get passive and active skills to help in battle. The part that gets fun, especially for those who have a mind for this, is the synergy between all of these different monsters.
There are about 10 different buffs and debuts, and there's one monster that gains a lot of passive stats by having buffs on it, but no way to buff itself. Another monster is a buff machine, applying multiple to your first, and then your third (as you fight with a team of 3) might have auras that allow buffs to stack multiple times, so your primary monster turns from middling to incredibly powerful by synergizing them in this way.
In addition, each of these monsters have different abilities in the overworld, leading you to need to collect many types to deal with platforming with flying up to obstacles, or breaking down walls, or even riding a monster to run over a crumbling bridge.
The story is present but it's...not engaging. It's about on-par with a Pokemon story in having you as a young, aspiring Keeper (Trainer) trying to find new monsters and help people out while dealing with an evil team before eventually facing the boss. It's serviceable to move the plot forward but you can pretty safely skip all of it and not miss much.
tl;dr: Metroidvania meets monster raising, with turn-based combat and intensive synergistic skill trees with a forgettable plot line.
But where it starts to get interesting are the monsters themselves. Each monster has innate strengths and weaknesses to different types of damage (physical, fire, ice, nature, wind, poison, etc. There are quite a few) similar to Pokemon, but the S/W are dependent upon the monster.
Beyond that, each monster, as it levels, has 3-4 skill trees that you put points into in order to get passive and active skills to help in battle. The part that gets fun, especially for those who have a mind for this, is the synergy between all of these different monsters.
There are about 10 different buffs and debuts, and there's one monster that gains a lot of passive stats by having buffs on it, but no way to buff itself. Another monster is a buff machine, applying multiple to your first, and then your third (as you fight with a team of 3) might have auras that allow buffs to stack multiple times, so your primary monster turns from middling to incredibly powerful by synergizing them in this way.
In addition, each of these monsters have different abilities in the overworld, leading you to need to collect many types to deal with platforming with flying up to obstacles, or breaking down walls, or even riding a monster to run over a crumbling bridge.
The story is present but it's...not engaging. It's about on-par with a Pokemon story in having you as a young, aspiring Keeper (Trainer) trying to find new monsters and help people out while dealing with an evil team before eventually facing the boss. It's serviceable to move the plot forward but you can pretty safely skip all of it and not miss much.
tl;dr: Metroidvania meets monster raising, with turn-based combat and intensive synergistic skill trees with a forgettable plot line.