Not every monster is intended as a threat. Some monsters are there to ease the player into the game at the start, keep him a little busy in between dangerous encounters, and back up more dangerous monsters. These non-threatening monsters are called fodder.
The best example of fodder is the Imp from the original Doom. Somewhat like a swarmer, they don’t have a lot of health, though still more than a swarmer. Usually enough to take one or two shotgun blasts. They throw slow-moving fireballs that are easily dodged, and don’t do a lot of damage anyway. While they’re often encountered in groups, they have no mechanism for attacking all at once, so it’s more like you fight a few at a time. The only threat in that case is if you have very limited space to work with.
So why do Imps exist, if they aren’t much of a threat? Basically, they’re used whenever the designers want to give the player something to do without challenging him much. Usually, as a break between encounters that try to kill the player, keeping him busy but still giving him a short rest. They’re also used very often to back up stronger monsters. For example, we often see a group of Imps with a single Baron of Hell, in Doom 1. The Baron of Hell is the main part of the encounter, but the Imps give us something else to worry about, to take our attention off of the main threat.
Fodder can also use some variation. The Guards from Quake 2, for example, are basically the same kind of fodder monster, but each has a little more health and different weapons. Quake 2 itself comes with blaster, shotgun and machinegun versions, with laser and ripper variants added in an expansion pack. Without much effort, they’ve added more monsters that are still familiar for a player; especially when these weapons mirror those the player has, himself. By necessity, fodder monsters have to be somewhat common throughout a game. When there’s enough variation, like with Quake 2’s Guards, it keeps the fodder from getting boring too quickly; especially when new versions are introduced more slowly over the course of the game. It also adds more flexibility for the designer to sculpt an encounter.
One more minor point about this, keep in mind that the player will be seeing a lot of fodder, so it’s a good idea to have even more variation. The Strogg Marine in Quake 4, for example, has more sounds than any other monster in the game, so it doesn’t play the same sounds all the time (which can get annoying).
Another fodder monster is the Grunt from Halo. Like the Imp, they have some weak projectile attacks, but they have some variation as well. In Halo 1, they could be equipped with either Plasma Pistols or Needlers, and there are Minor (basic, yellow-armored), Major (red-armored, more health and can throw plasma grenades), and towards the end of the game there are Special-Ops Grunts (black-armored, even more health and almost never panic). Often, they’re seen backing up Elites, the major threat of these encounters.
The big difference between this and the Imp, however, is that these guys drop their weapons, giving the player a source of ammo. Similar to Combine Soldiers in Half-Life 2, or the basic Former Humans in Doom, they act as a method for the player to resupply, but the player has to do something to earn it. This gives them another function alongside what fodder already does.
There is one major variation of fodder, and that is the basic meat-shield. The Demon from Doom is the best example of one, though the Headcrab Zombie from Half-Life 2 is one, as well. It has a lot of health, but only has a melee attack that doesn’t do a lot of damage, and can only hit with if it pins you against a wall. Unless very strategically placed (There are some traps in Doom 2 that take advantage of them, most notably in “Tricks and Traps” and “Downtown”), they aren’t particularly dangerous. All they really do is rush at you and absorb damage.
They have most of the characteristics of fodder, but they bring something else to the table in that they can drain resources. Somewhat like tanks, they drain either ammo, time, or especially space in an area, but unlike true tanks, they don’t really demand your attention like they should (either by being threatening or having some annoying mechanic). There are some meat-shields that have ranged attacks, but usually those are low-damage or easy to dodge in any case (though some consider Doom’s Baron of Hell this, despite its high damage). They do add a bit on the mechanical side, but they can be pretty boring for the player.
Like the Imp, these fodder monsters are there to keep the player busy while giving him a break. In the case of enemies like Halo’s Grunt or Doom’s zombies, they can also give the player ammo and weapons without simply having them lying around (he has to earn it). Sometimes, as well, they’re a minor challenge after giving an important item, but without actively trying to kill the player (for example, the Imps after you get the shotgun in Doom 1’s Hell Keep level). They also give the player the ability to ease into gameplay slowly at the start, letting him get used to controls and other mechanics. Many games these days (Crysis, for example) omit the fodder role entirely, and I think that’s a mistake. Games that don’t have fodder at all either don’t give the player a break, or have downtime where absolutely nothing happens. Fodder is best used to help the designer control the flow of gameplay like a sonata, with high-action and low-action segments, as opposed to high-action and no-action.
There are cases where fodder doesn’t really help. For example, I don’t think fodder works well in survival-horror games; weak monsters tend to give the player a feeling of complacency, making him feel like he can handle whatever the game throws at him. Dead Space’s idea of fodder, the Slasher, is capable of killing the player, it’s just easy to deal with unless it catches him off guard. Fodder works best when your game uses multiple, different roles of monsters.
Every once in a while, some games give certain kinds of fodder some incredibly-powerful ability, like Grunts Majors and the basic Chaos Heretics from Space Marine both have the ability to throw grenades. This is mostly some attempt at keeping the player on edge, because this group of easy monsters can actually kill him if he’s careless. However, it really depends on the pacing and mechanics of the game in question; for example, this works well in Space Marine and Halo because it’s easy enough to dodge, but it could never work in a game like Doom. Doom is just too fast and hitboxes are too easy to hit for this to work. It also works because not every fodder monster in Halo and Space Marine has an ability like this; it’s just the red-armored Grunts in Halo, for example. It would be annoying and overpowered if every Grunt in Halo could throw plasma grenades, and it gives more meaning to that variety besides slightly-increased health.
When fodder monsters do have nothing but powerful attacks, they’re what are commonly known as glass cannons. The best example of this that I can think of are the Special-Ops Grunts with Fuel Rod Guns in Halo 1. Again, among the weakest monsters in the game, but suddenly has a weapon that can instantly kill you if you don’t see it. These surprisingly don’t work very well, but usually a game can get away with one if it’s well-used. The problem with glass cannons is that they’re pretty luck-based. If the player spots them, he can kill them quickly and they aren’t a problem; if he doesn’t, then he takes a lot of damage. The upside to this is if the glass cannon is a variant of an existing fodder monster, like the Special-Ops Grunt; we know it’s going to be easy to kill from experience, but suddenly it has a much bigger gun, so we immediately know exactly how we should handle this. Also, for balance reasons, its gun explodes when it dies, so the player can’t use it (which nullifies the ammo-giving mechanic of Grunts). I’ve heard arguments that the glass cannon could be considered its own role, but it doesn’t have enough characteristics on its own to warrant that, so I figured I would talk about it here. I will be expanding on this in future monster role articles, as it applies.
There are enough similarities between swarmers and fodder that you could say that swarmers are fodder that simply has some way of taking advantage of their numbers. Certainly Halo’s Grunt and Drone aren’t very different aside from the Drone’s mobility. Because of that, you can use swarmers as fodder by just reducing their numbers enough to where they don’t really swarm. I still like seeing an individual kind of monster as dedicated fodder, but using swarmers as fodder is good to mix things up. This is also a warning; if you make a swarmer you should make sure it is actually dangerous in groups, otherwise it’s just fodder.
Except for that, though, the fodder role isn’t as compatible with any other role (as a dual-class monster). You could never have a fodder/support; that’s just a support. Because tanks have to be threatening or annoying enough to demand your attention, the closest thing to a fodder/tank is a meat shield, and that’s not particularly good at being a tank anyway because they don’t do that. However, fodder works very well in encounters alongside those kinds of monsters. How many times in Quake 4 do we see Strogg Marines backing up a Gladiator or other strong monster? We also have the Scanner in Half-Life 2 supporting pistol-wielding Combine soldiers, making them a bit more dangerous than they would normally be. Fodder often makes up the meat of encounters, after you decide what roles should be central.
I hope this shows how important the fodder role is to actual gameplay. As I said, most games these days skip this entirely. If you’re designing a game that uses different roles of monsters, you kind of have to add in at least one variety of well-designed fodder. Without them, it can be a lot harder to control the flow of your gameplay.