The C'tan on the tabletop

 I've now had some time with C'tan on the tabletop.  I spent some time brainstorming how best to use them.  I've run them, run up against them, or watched them a chunk now.

So You Brought a Centerpiece

A C'tan is a hefty chunk of points - 350 points of mortal wounds, love, assault power, and battle-dictating survivability.  Simply by being on the table, a C'tan begs a question of the opposition - "Do I try to kill it, or do I try to feed it chaff?"  Some armies just aren't going to have chaff, and they're going to have to figure out how to handle the C'tan.

Stumbling Blocks for the Centerpiece

Note that C'tan are vulnerable to crap rolls - if you fail a power of the c'tan, you can't re-roll it.  Similarly, bad melee rolls make you cry - anyone that can degrade to-hit rolls or mess with wound rolls is liable to give your C'tan a bad day.  Similarly, anyone with the ability to mess with charge rolls can give them a bad day.

Of particular note are any units that have innate rules or stratagems for wound rolls - dropping to a 4+ to wound due to Quantum Shielding or Transhuman Physiology is a big deal.  

Note also that 3W infantry are in a weird spot for C'tan (other than the Deceiver) because you're looking at 1d6 damage per hit (or flat 1 for the Nightbringer's sweep attack).  Even if you blow through their saves, you still have a 50/50 chance of killing them with random damage.  2W infantry aren't as big a worry unless you're the transcendent C'tan, the others can generally power through.

None of the C'tan are really thrilled at the thought of chewing on a horde of models, but you brought support for that, right?  Like seriously, My Will Be Done on a bunch of warriors and a veil is a pretty reasonable investment.

Command Points and C'tan

Seriously, be prepared to burn several on a C'tan.  You should consider the 1CP 'use a random power' stratagem - this is part of your damage output.  It might or might not work, but it's decent investment.  If you brought the Void Dragon, it's not unreasonable to think about a CP for a re-roll in the shooting phase.

For the dead gods' sake, save one for the charge.  Failing a charge with a C'tan is a significant blow.  

Keeping one around for a re-roll of a 4++ is an iffy thing at best - it depends largely on what the dice do.  If your opponent has decided the C'tan should be dead, then a timely re-roll may result in you drawing fire that could maim other stuff in your list.  The C'tan puts the opponent on a schedule, and missing a wound in a phase can be pretty important.  Taking hits back in melee depends largely on matchups you should be dictating.

Chip Damage and Army Composition

Something else I've noticed in the shooting phase - if you have a heap of units, it's not too hard to chip off the wounds.  And here's where army composition comes into play.

Necrons brought C'tan, only infantry - all the anti-tank goes into the C'tan until 3 wounds come off.  This isn't a bad outcome, but it's nicer if you're absorbing higher rate-of-fire weapons that would otherwise go into your multi-wound models

Necrons brought C'tan, other targets (IE - vehicles, Destroyers) - now it gets interesting.  Your hope is that the C'tan's 4++ absorbs the bulk of the firepower.  Alternatively, you bring something beefy along with it - charging monoliths are uglier than you think.

C'tan vs. small arms - you are T7, 4++ (Void Dragon gets a 3+/4++, but AP-1 isn't THAT rare) - S4 gunfire in small chunks is actually user-friendly on your opponent - three failed saves from boltguns are just as useful as a dozen.

Strategic Reserves?

Gut says 'no' on this - and here's my logic.  The instant a C'tan hits the table, it dictates the fight.  It moves, it drops mortal wounds, and unless it's turn 1, it's probably in assault.  Hell, if the enemy moved towards you at all, you might be in assault already.

Now, pull it off the table.  On the bright side, the enemy can't shoot it, and you can keep them guessing, right?  Well, first off, you're giving up C'tan powers.  Second, you have to come in off a board edge - if the enemy focuses on a flank, congrats - they get to dictate your deployment, which is the opposite of what C'tan should be doing.  Third, that's a turn that the C'tan isn't really contributing - you're down 2CP for the reserves, and should assume you'll want a third CP for the charge re-roll.

Did Your Opponent Bring a Balanced List?  Did You?

Realistically, this is the biggest question that you'll run into.  If the opponent is relying on one phase to do the bulk of their damage (IE - Tau/IG for shooting, demons for assault, etc.) then they'll hate the C'tan.  If you can avoid getting tied down, great.

If your opponent brought a list that can do damage in 2-3 phases easily (IE - they have psykers, guns, and melee weapons) then they're in a reasonable position to kill the c'tan.  You'll definitely want to pay attention to what it fights, and if you can seriously mess with the enemy's ability to hurt you in a phase (IE - murder a psyker or two, because the dead don't smite) then go for it.