There are only three character classes to choose from in Harbinger: human, gladiator, and culibine. The gladiator is a cyborglike robot infused with the consciousness of a living being, while the culibine resembles Diablo's sorcerer character, though in practice, all the classes play about the same. While the different classes have special gadgets they can use--the gladiator can control remotely operated cameras and the human can drop mines of varying types, for example--these items actually don't figure prominently into the gameplay because of play-balance issues between the attack types.

All three classes have a ranged attack, and the human and gladiator have true melee attacks. When engaged in close-quarters combat, the culibine can use a spell-like ability to damage enemies in a small radius around her. However, almost all ranged attacks from enemies in Harbinger are slow projectiles that are easily dodged. You can also outrun just about all the enemies in the game. As a result, you'll find that the entire game consists of running away, firing off a couple of shots, dodging your enemies' shots, and then running some more. There is no point in putting yourself in harm's way by moving into melee range when you can avoid damage altogether by just running and shooting all the time. While you could argue that this kind of shallow gameplay is a feature of almost any other game of this kind, Harbinger lacks the fun elements that better action RPGs possess.​