Named after the titans of old our monstrous heavy supports are certainly very interesting units. Lets take a look...
Chronos pain engine
Relatively cheap for its stat block it's a great starting block, for just a few more points you can have access to a great flamer and a good blast weapon. Having 1d6 hits and then 1d6 shots both at str5 and -2 save with a possibility to jump up to damage 2 is great damage.
In melee they are a very interesting unit, as a buff bot they allow nearby core/character units to re-roll 1's to wound which is a very solid buff and since they are core it applies to them too!.
The spirit-leech tentacles are where things really become interesting though and they are what allow the Chronos to do it's real job. For every model the Chronos kills in melee you can heal a core unit within 6 inches or if the unit has no undamaged models you can return a model to life. If taken cheaply a 210 point unit can stay in the fight a long time against anything that isn't wielding lots of power fists or the equivalent. Things that will struggle to wound them will never kill them in melee and at toughness 6, 3+ armour a 6+invun and +5 fnp that's a big list of things.
They also have their own stratagem which lets a unit nearby units jump right to level 5 power from pain for the rest of the battle. That's a really serious buff!.
Our dreadnaught analog, it's kind of versatile it has access to allot of different load outs. It's hard hitting if somewhat inaccurate luckily all of its guns come in banks of 2(well except the stinger pod). Depending on what you want it to kill a Talos can be given a loadout to match.
Vehicles/monsters the heat lance or haywire blaster are good options with the heat lance being the most reliable. Splinter cannons are good vs MEQ and stinger pods let you advance and spray light infantry.
In melee you come with 2 macro scalpels for 7 attacks and MEQ slaying madness with options to swap one or both for other weapons. The gauntlet lets you hit tougher targets like gravis or vehicles you loose some attacks but get a good return in damage for it I think, nobody likes the threat of damage 3 vs their most expensive models. In the same slot you can instead slot the chain flail a weapon that lets you double up your attacks, it doesn't have the same hitting power as the other melee options here but it does allow for a unit of Talos to throw out 30 strength 6 attacks which is kinda scary throw enough of that at a brick wall and it will stick. The last weapon options are the twin liquefier gun you are all aware of (DT madness) even without DT its still great, and the ichor injector a personal favorite d3 mortal wounds on a hit, even though you can only make 1 attack with it it hits on 2+ after turn 3 or if you are dark creed with a trophy raider near by.
So coven synergy wise there's allot of obsessions that buff both monsters, dark creed helps with accuracy and for 3 cp you can ignore look out sir, 6 heat lances at a character is scary, and the Chronos shooting can just put him out with weight of fire. The coven of twelves bonus ap help make wounds stick.
As for other covens artists of flesh can force your opponent to allocate their lascannons to your Talos/Chronos rather than their other lighter guns, even power fists loose allot of their hitting power. Experimental creations add one to the strength of both models which is a good general purpose buff. Master tortures' lets them reroll to wound for free in melee and my favorite spliterblades, Double hits on 6's works really well with the ichor injector 2d3 mortals is pretty rough.
Both units really preform in their roles very well, it's interesting how well they designed they are if I wasn't planning of running full kabal/BFH they would defiantly be allot of fun to field.
Those are all my thoughts on these units for now, things might become more interesting if coven gets an expansion.
Next up the Ravager.