The Four Star Syndicate is a mercenary organization that is known for taking contracts against the Mercarian League. Even though it seems to employ a wide variety of mercenaries and thieves, the leaders of the syndicate remain largely unknown.
A Four Star Syndicate army is composed of Mercenaries who will work for Khador or Cryx.
What to Order
A Battlegroup does not currently exist for the Four Star Syndicate. However, you can build an 11 point starter by beginning with a wanted man.
NOTE: For a while a battlebox was available containing the exact models in the list below, if you search eBay or other second-hand sites you may be able to find it for sale.
Magnus the Traitor

Singularly the biggest threat to King Leto's reign and Cygnar as a whole (after that Draconic Elder God living offshore), Asheth Magnus is a tactical genius. His Feat allows you to either cross the board in one turn at the cost of being unable to attack, pull out of unwanted combats, or bypass the enemy's front line and get 'jacks into their squishy parts. Magnus's sword is focus efficient for boosting ensuring that when he hits a target he needed to boost for, said target will take a crap-load of damage. Also for close combat you can use his bionic arm which comes with Knockdown making him a good partner with the Renegade or Mangler. Lastly he has a scattergun which is somewhat better then the generic pistols used by other 'casters
Talon
Of the three 'jacks in this list, the Talon is probably the weakest, by dint of costing 2 points less than the Renegade, but being far inferior to that warjack. Its not too bad if you can get it to to charge an enemy warjack, as the Stall property on its Stun Lance means you could probably keep the 'jack tied up for a few turns while the Renegade or Mangler take down the opponent's more important assets. Overall this isn't so much a bad warjack as it is overshadowed by its peers.
Renegade
This is probably the best light warjack in the whole game, its got an arc node, its melee attack has both Sustained Attack and Critical Shred. The obliterator rocket alone makes it worthy of inclusion. When you attempt to expand from this list consider getting another one and use them in a tag-team fashion where one knocks down the target with the obliterator rocket and the other charges the now auto-hit target to unleash a chainsaw execution. If you intend to take the Magnus the Traitor theme list, then you will need a second one of these badasses.
Mangler

A nice heavy, good ARM, but Khador-like DEF, just about the best thing with this one is its Wrecker, which has Thresher, good little combo with the Obliterator rockets on the Renegade, simply knockdown the target unit, charge the Mangler and bypass its average MAT, straight to rolling the nice P+S of 17 against everything in its front arc.
Tactics with the Four Star Syndicate Starter
A very basic tactic, recommended for beginners, is to pop Magnus's Feat in the first turn and run your whole battlegroup so that you the cover 20" between your opponent and you. This is good if your opponent is more shooting oriented, needs a free turn to get upkeeps setup or requires the charge, as at 20" you should be too close for them to make a proper charge move. The downside with this is that you then spend a whole turn sitting in your opponent's face without having done any damage etc...
The more mundane tactic is simply to get into combat with your opponent's front line, then pop the feat and bypass the defenders and bring your 'jacks up to the 'caster, ignoring Freestrikes.
Other alternatives is to run the Renegade(s) up, shoot then use the feat to fallback or flank, while the Mangler, supported by the Talon, smashes the knocked down units and then uses the feat to threaten another unit/model.
Beyond the Starter Set
The first step to expanding this list is to get a second Renegade, its a great warjack and its only real limitation is that only 2 can be fielded. If you want to take advantage of the bonuses in Magnus's theme list (who doesn't want to start the game with free upkeeps that cost nothing to maintain?) then consider any combination of the Steelhead units, Halberdiers make a good melee unit, the Riflemen, while subpar to Trenchers and Long Gunners, they are capable of provide decent support to Steelhead Halberdiers or Cavalry.
Speaking of Long Gunners and Trenchers, Magnus the Traitor allows you to take a single unit of either, but not both, provided your army consists only of models in that are allowed in a Magnus theme list.