The Cadmus is an AD trooper that starts in a special Seed Embryo state. Instead of starting as a S0 camo token, it begins as a S0 model with a free land mine on the same location. This means that when it arrives via combat jump it will be S0 and still need to hatch. It can do so by a Short skill or by waiting until it's next turn.
The Cadmus has decent stats and some basic weapon options including a Boarding shotgun and the coveted LGL which can be very deadly on a drop troop. To supplement it's stats it also has Morpho-Scan which allows it to Short Skill: Scan any model within its ZoC and for the rest of the game copy their MOVE, BS, CC, and PH stats. You can also scavenge an enemy model's weapon just like with Scavenger or Booty, which can give the Cadmus an offensive boost.
While order intensive, a Cadmus that lands well, and copies a superior trooper can be a beast to deal with.
Starting in the Seed Embryo state means that this troop will AD at S0 meaning it will prevent more ARO than normal when dropping. It's special mine option will protect it while it is in Seed state and it's Seed profile is harder than normal being AR 3. Once hatched, it is just like any other trooper.
A special note should be made that Morpho scanning can result in better stats which can allow for better ARO rolls.
This profile has the Spawn Embryo rule. When the unit is unconscious, it still counts as a scoring unit for scenarios like Quadrant Control or Supremacy. Armies with large numbers of Shasvastii might consider taking out enemy units with Shock, Viral, or Monofilament as a higher priority to exploit this rule.
Morpho scan has already been discussed above. It is a trick no other army can preform to date. Don't forget that you can also scavenge an enemy model's weapon just like with Scavenger or Booty, which can give the Cadmus an offensive boost.
The LGL profile can drop into good range and proceed to rain grenades on enemy models from out of LoF at 8s to hit. If you morpho scan a target you can increase your BS and make this more deadly, or use it with a FO to get up to BS 17. This is particularly worth the orders if you can pinpoint and kill a squishy enemy lieutenant or attack REM or Motorcycle models that dodge at -3 and -6 respectively.
Because the Cadmus starts with a mine, it is possible to drop it behind enemy models to prompt them to Turn to face, then move another model up to shoot the enemy from a different direction. If far enough away you can prevent an ARO all together but if the enemy does get a chance to dodge they now must dodge both the mine and shot or take another ARO and accept the hit from the mine.
Like any AD, it is good to have a few models watching your flanks.
This profile has the Spawn Embryo rule so when unconscious, it still counts as a scoring unit for scenarios like Quadrant Control or Supremacy. You can bypass this by killing them out right with Shock, Viral, or Mono-filament, or by killing the unconscious models. Shasvastii players may focus extra attention on your sources of shock. Try to use that to your advantage.
Cadmus will often be an after thought to a list. They are too expensive and order intense to take in great numbers. They will, however, benefit from scenarios offering a bonus to AD troopers, perhaps more than most AD because of their unique S0 state.
If you are bringing fraakta, Rasyat, or Ko-Dali, it can also be nice to have a Cadmus for the mine trick (see tricks section) which can help other AD land.
This option is somewhat unpopular in CA and it is unlikely to be on your opponent's crib sheet, so there is something to be said for surprising play.
This model MUST deploy via AD: combat jump since Seed Embryo is not an optional skill - if you choose to deploy it via AD (can't downgrade skill to airborn infiltration for example).
But remember you can choose to deploy it in your DZ during your deploiement phase
Active Turn Role
The Cadmus is an active turn piece. It is meant to scan something powerful and rambo the enemy back line. It can also be played as a LGL platform focusing on using AD to drop to a good position and speculative fire at models Targeted by your FO units.
In Seed Embryo this model has higher armor and a one shot mine. This should not be considered a perfect defense, and it is best to spend the order and hatch this unit before the enemy turn. If you are in a good position (say on a roof out of all enemy LoF it can work to have this model Hatch as an ARO, but it is still riskey
There are no other special ARO actions to note over any other trooper.