Activating a basic or Elite unit behind an identical unit which is already charging will 'fuse' the two, doubling their attack power and adopting the better of their two countdown times. The other tactical option is 'linking', when two activated units of the same colour, although not necessarily type, share the same countdown timer. Any units of the same colour who attack on the same turn will also have their attack power multiplied.
At the end of each battle you collect resources and experience, with both the hero and individual unit types adopting a simple RPG levelling system, while resources buy replacement Elite and Champion units.
Overall it's a pretty complex system, and one which will take a couple of hours to get used to. Picking which troops to take to battle is a vital part of strategy too, as you decide whether to focus on speed or power, attack or defence. Multiplayer games see a further level of customisation in the choice of the five very distinct yet excellently balanced factions.
This depth is initially confusing and indeed frustrating. Trying to follow the developments on-screen as your opponent seemingly racks up endless magical combos, sweeping your tentative strategies from the board, is tedious business. Once it clicks, however, Clash of Heroes begins to reveal just how much it has to offer.
For example, you notice how important it is to remove pieces. Erasing single units causes those above to 'drop' towards the centre line, activating chain reactions and granting you extra moves before control switches back across the board. These tactical gambits, rendered ever fragile by the possibility that they'll be utterly destroyed before they reach fruition, are incredibly satisfying to pull off, and can turn a battle in your favour. In fact, recognising when a turn can be saved by the judicial use of this mechanic is probably the most important thing you can learn.
Hidden areas and secret units dot the environments, which are presented in classic Heroes of Might & Magic map-node style, whilst side-quests break up the narrative action. Another interesting addition are the battle puzzles: set-pieces which see you up against a formation of enemies who must be destroyed in a single turn with only a limited number of your own troops on the board. These are the most mentally intensive of COH's challenges, requiring substantially lateral thinking.
This being Might & Magic there are some familiar gripes among all this praise. Difficulty spikes crop up a little too often, and occasional boss stacking with no chance to save in-between is a low blow. Grinding is a necessity for all but the most gifted too, although battles never really become repetitive, forced as you are to adopt new strategies according to the lay of your armies.
The AI also makes a few strange choices, despite generally playing intelligently enough to offer a decent challenge without resorting to Puzzle Quest's 'convenient' enemy gem sequences. Chance is an obvious element too, and can be irksome when fate's fickle finger falls awkwardly for you, but defeat simply means a very quick reload and another try - chaos giving you the eventual edge in the war of attrition.
All the same, the campaign is huge, with five factions to command through a storyline of solid if unremarkable fantasy guff. There are a good 30 hours of single-player action alone for a talented and lucky player. Add to this the limitless possibilities of multiplayer - accessible with a single cartridge and two handhelds - and you've a huge chunk of game.
During the course of writing this, Eurogamer MMO editor Oli Welsh popped up on my MSN to ask me if I thought it was a puzzle, RPG or strategy game. It has enough elements of each that I honestly couldn't say. What I did do was recommend it to him wholeheartedly, because, whatever it is, Clash of Heroes is a very good game indeed.
Might & Magic: Clash of Heroes is out now in the US and will be released in Europe on 22nd January.