Games Workshop's Warhammer 40,000 universe is very well known, and a familiarity with its massive volumes of lore will definitely help with immersion... but by no means is it essetional. For the uninitiated here's a very quick summary: "Human Space Marines good. Rampaging insectoid aliens bad. Purge the alien filth!" In fact that's pretty much the plot in a nutshell... and tbh what more do you need?
Deathwatch really goes back to what GW does well; good old fashioned small squad turn based strategy action. It's very much in the vein of classic board games like Space Crusade and Space Hulk. You have a personally selected squad of 5 Space Marines with which to wreak vengeance upon the Tyranids. Each unit has a set number (usually 4) of action points (APs) per turn. Most actions (move 1 square, attack) cost 1 AP, but some (mainly firing a heavy weapon) cost more. All pretty simple so far. But things get more tactical when you introduce Overwatch. In your turn you can use 1 AP to set a marine on Overwatch, where he will stand guard and use the rest of his APs in the enemy turn to fire at anything that crosses his line of sight. This is a crucial mechanic, as it allows you to set up defensive positions and wait for the enemy to break cover.
There's plenty of variety in squad selection. Marines come in 4 different flavours:
- Assault - the "up close and personal" approach, equipped with a short range pistol and melee weapon
- Tactical - the "all rounder", generally specialising in short to medium range guns
- Devastator - long range death with a heavy weapon
- Apothecary - the medic; another short range/melee specialist, but who can heal teammates
Cards come in 4 tiers of rarity/quality. In general high tier stuff is better than low tier of course, but it's not quite that simple. Marines have abilities to unlock, and a high tier marine will have a lot more than a low tier one... but all this does require a lot of experience. Experience can be spent on unlocking skills, wargear slots or levelling up the basic stats: health, accuracy, critical chance. A top tier marine will have a lot of upgrade options, but will take much longer to get them all.
Weaponry levels are very important too. Low tier weapons have low damage, but high accuracy. High tier weapons have much better damage and other bonuses, but generally very low accuracy. As a result high tier weapons are almost completely unusable by newbie marines, as they just won't be able to hit anything until they've pumped up their accuracy a lot. However, once high tier weaponry becomes reliable it's devastating! It's a good system, as it means that decent equipment must be earned - you can't just kit out a new guy in high tier stuff.
It doesn't take too long to get a new guy off the ground. Each marine typically earns 1-2K experience per mission, and the first few levels are very cheap... but some of the better skills get very expensive, even up to 20K in some cases. Which is fine... so long as you can keep your marine alive. If a marine dies in a mission then all his experience balance is lost. Early on this isn't too bad, but in the later stages losing 12K of banked experience can be painful. Spend it while you can, as you never know wht the next mission will bring
As you may have noticed I love this game. The concept is simple, but the layers of tactical depth are immense. I'd very highly recommend it to any fans of the genre