I'm not strongly into tower defense (TD) games, but this game does away with some of the downsides of tower defense games which bother me. Your towers are characters you gain as you progress in the story, or purchase at various points. Your team protects your summoner, and both the characters and summoner, gain XP after each battle (win or lose, although that can be adjusted). If the game becomes too hard, you can replay an earlier level for extra XP / scrap (the game's currency). However, replaying levels is not grindy-feeling, since each level can be played at three different difficulty levels, which is a different than just the same monsters with more HP (for example, sometimes there are additional spawn points and sometimes the monsters have additional bonuses). (And if you really don't like redoing levels for XP and scrap, you can increase the gain of each of them.)

Unlike some TD games, there is no pathing manipulation: the squares the characters can be placed on are different than the creeps' travel squares. That doesn't mean that character placement is permanent: it is sometimes useful to remove and re-place characters (especially in boss levels or the bonus levels available during the second playthrough).

Speaking of the second playthrough, that isn't just the same monsters, but more HP. Usually the second playthrough monsters have additional abilities, such as attacking your characters as they walk by, or become temporarily immune to non-area damage. The second playthrough also allows purchase or unlock of the best weaponry. Another nice touch is that switching between the first and second playthrough is just a matter of returning to the menu; your entire party and loot remains the same. (I worked a bit on the second playthrough, got stuck, went back to the first playthrough to do some of the harder difficulties of the levels, got stuck, went back to the second playthrough, et cetera.)

Besides your party characters, the summoner has a few spells that unlock while progressing through the story and can be increased as the summoner's level increases. These spells can help out during tight spots in earlier levels, and are pretty much required for the hardest levels.

Slak says to at least try the demo; pants are optional.

I'm not strongly into tower defense (TD) games, but this game does away with some of the downsides of tower defense games which bother me. Your towers are characters you gain as you progress in the story, or purchase at various points. Your team protects your summoner, and both the characters and summoner, gain XP after each battle (win or lose, although that can be adjusted). If the game becomes too hard, you can replay an earlier level for extra XP / scrap (the game's currency). However, replaying levels is not grindy-feeling, since each level can be played at three different difficulty levels, which is a different than just the same monsters with more HP (for example, sometimes there are additional spawn points and sometimes the monsters have additional bonuses). (And if you really don't like redoing levels for XP and scrap, you can increase the gain of each of them.) Unlike some TD games, there is no pathing manipulation: the squares the characters can be placed on are different than the creeps' travel squares. That doesn't mean that character placement is permanent: it is sometimes useful to remove and re-place characters (especially in boss levels or the bonus levels available during the second playthrough). Speaking of the second playthrough, that isn't just the same monsters, but more HP. Usually the second playthrough monsters have additional abilities, such as attacking your characters as they walk by, or become temporarily immune to non-area damage. The second playthrough also allows purchase or unlock of the best weaponry. Another nice touch is that switching between the first and second playthrough is just a matter of returning to the menu; your entire party and loot remains the same. (I worked a bit on the second playthrough, got stuck, went back to the first playthrough to do some of the harder difficulties of the levels, got stuck, went back to the second playthrough, et cetera.) Besides your party characters, the summoner has a few spells that unlock while progressing through the story and can be increased as the summoner's level increases. These spells can help out during tight spots in earlier levels, and are pretty much required for the hardest levels. Slak says to at least try the demo; pants are optional.