Once Upon a Knight must have been imagined as something other than a typical real-time strategy game. An obvious amount of effort went into fleshing out the RTS and RPG elements in two separate modes, each with its own campaigns, but the resulting hybrid isn't a good example of either type of game. Apart from odd attempts at humor that are hard to ignore, the story execution falls flat, the scenarios are tediously scripted, and the skirmish mode is terribly limited.
The far-off, long-ago fairy-tale kingdom of Prince John is a land troubled by the despicable lord Valtamand. The prince, who is naturally all things good and honorable, was kidnapped by Valtamand, and that predictable premise sets up both a series of RPG scenarios in which a single adventurer attempts to free him and a real-time strategy campaign that has you controlling the prince in his effort to regain power after escaping. The modes are completely distinct--like two thematically similar games that happen to share the same look, monsters, and control scheme--and if the long campaigns don't happen to offer enough material, there's multiplayer support for both.
The three campaigns are made up of story-heavy puzzle-based missions and some large battles.
After navigating all these options at the main menu, you'll find that the real-time strategy campaign has the most to offer, which isn't surprising given Reality Pump's background as the creator of the Earth 2150 series. The main gimmick is that the game's economy is based on milk produced by grazing cows, and for some reason, this is supposed to embody the game's overall humor. In reality, it takes quite some time for the campaign to even work up to a typical base-building mission, as the early chapters predominantly focus on quests for items and puzzles that most often involve searching the map--sometimes above and below ground--for buttons to open gates. There are usually enough hints in the in-engine cutscenes or the goal list so that the quests are incredibly straightforward, and marks often appear on the minimap to make things even clearer.
These missions are typically quite short and provide more than enough time to get accustomed to the controls and rotatable 3D camera. Yet, the pacing is uneven, and suddenly you're in the middle of an early showdown with Valtamand in a long multipart mission. Even combat-focused scenarios like this often include the largely annoying puzzle elements, though. Nevertheless, these relatively action-packed missions are the best the game has to offer, and the larger battles can involve dozens of units on either side. Adventuring has a number of important secondary benefits, providing ample opportunity for units--most importantly, Sir John and accompanying main characters--to gain experience and significantly upgrade their weapons and armor. When it works well, the mix of questing and combat helps cover the relatively slow speed of unit and base building, something that's much more apparent in skirmishes.