Early on, we knew that the monsters in Dungeon Rancher would have abilities if only to differentiate them from each other. There are four resources players use to feed monsters. Since each monster uses two resources, this implies a total of 4 choose 2 = 6 monsters. We gave the Dragon and the Golem simple resource production abilities to start with while testing other aspects of the game.
It wasn’t too long before we added abilities for the rest of the monsters as well. One useful principle we discovered is that abilities that don’t require keeping the monster around are unthematic because they make the monster feel more like a resource card than like something to raise. For instance, one version of the Golem’s ability allowed players to discard it to build a room for free, so players treated it like a “free room” card and always used it immediately.
We settled eventually on the concept that each monster would have a different scoring ability. After some experimentation, we further determined that such scoring abilities should always force the player to take on risk for more points. For example, the Dragon scoring ability increases its value for every ‘6’ on it, making it much more difficult to tend. Under this system, creatures represent different ways for the players to challenge themselves to increase their score.
The newest addition to the monster mechanics rewards players for placing monsters with matching “personalities” in adjacent rooms. For example, placing a creature with a food symbol on its right in a room to the left of one with a matching food symbol on its left produces a single food resource, which is automatically useful since you have two monsters that require it. The objective was to make monster placement more interesting. Adding this mechanic costs very little because it echoes the existing mechanic that adjacent matching rooms produce magic resources.