Let's say I have a Tactical Squad Cardinis in play and I use their area effect ability. Am I then able to follow up with The Fury of Sicarius and kill every enemy unit at the planet, that was damaged by the area effect?

No.

Per the Rules Reference Guide for Area Effect [X].

This damage is considered to be dealt by a card effect. It is not considered to be dealt by the attacker's attack, but it is being dealt while the unit with Area Effect is attacking. After the Area Effect ability has resolved, the attack is over.

The Fury of Sicarius triggers off of a unit being damaged by an attack. Area Effect damage is not dealt by an attack, it is dealt by a card effect, therefore you cannot even use The Fury of Sicarius in this situation.

Note that even if it could be used in the situation (as Minute says, it can't), you'd need one reaction per unit you wanted to kill. The single event, which reacts to a single unit being hit, could not be used to kill all units that were hit by the AoE at the same time.

Off topic here, this card did a lot of damage to me last night. It's never fun to see your Soul Grinder have to eat it after an attack from a 10th Company Scout or a Khorne Berzerker go down after one measly swing from Sicarius.

Off topic here, this card did a lot of damage to me last night. It's never fun to see your Soul Grinder have to eat it after an attack from a 10th Company Scout or a Khorne Berzerker go down after one measly swing from Sicarius.

Yeah, nothing like a weenie KOing a fatty....lol

Off topic here, this card did a lot of damage to me last night. It's never fun to see your Soul Grinder have to eat it after an attack from a 10th Company Scout or a Khorne Berzerker go down after one measly swing from Sicarius.

Its a tough one to deal with, and the sort of thing that SMs do best.

Things that might help:

First, remember he's only got two of them. You can judge the odds that he'll have it in hand by how many cards he has in his hand, how far he's gone into his deck, and if he's played one already.

Second, it costs 2 resources. If Cato's player has 2 resources back, always remember he might play it.

Third, be wary when it looks like his Warlord ought to retreat, but he attacks instead. Typical scenario: you have a Heldrake, he has initiative and Cato. On his attack, he doesn't retreat with Cato. Interpretation: He has Fury of Sicarius in hand. This ties into the next point:

Fourth, its conditional on the attack successfully dealing damage. If you think he's likely to be about to play Fury, then now is the time to shield that damage down to zero. This is tough sometimes, as Chaos only has access to one 2-shielder card right now, but as a rule of thumb, when playing Space Marines hold on to Tzeentch's Firestorm as it's shields may be the brinksmanship play that keeps your daemon in play for one more turn (and often the game win). On a similar note, you should almost never play your 3-shielder for effect when going Chaos against Cato.

Fifth and finally, don't forget its non-Warlord unit. If you think its very likely they're planning Fury, then sometimes adding your Warlord to the battle is enough to clinch a win.

He actually had both of them in hand at the same time, and used them in successive attacks. I had my suspicions, as he had passed with four resources left and several cards in hand. A bloodied Sicarius is committed. The pattern was there. Unfortunately, there was nothing I could do, as I was holding only one shield card(Infernal Gateway). I could not have possibly prevented all damage in either case.

Ironically, keeping Sicarius around almost cost him the game as I played Infernal Gateway when all units were exhausted and dropped in an Alpha Legion Infiltrator. I took aim at Sicarius(he had one damage on the bloodied side) and would have won except he was able to shield one damage. It was that close.

Yeah, sometimes you know they're going to play it but you can't do anything about it anyway. Dems da breaks!

Sixth tip, to add to the ones above, is to remember that Cato may be great at generating resources but he may struggle to draw cards. He'll have his six one-cost neutral cappers, and will be depending on his allies otherwise. If you concentrate your command phase on denying him card draw you can often keep Fury and Indomitable out of his hand.

Its well worth losing a Flamer to take out his 2-command presence on a +cards planet, even if this can be inefficient.

Also, of course, as Chaos you want to keep the game short. The fewer turns the game goes on, the weaker the Space Marines combat tricks are. Force him to play a whole game with 20 cards and there's a 35% chance he'll never see a Fury of Sicarius. Get him to play a whole game with 15 cards and push that to 49%. Best case scenario, and play 3 turns where he never wins any cards from command, and there's a 61% chance he won't see Fury. On the other hand, play one of those 7 turn games where he has 15 cards left at game end, and there's a 91% chance he'll see 1 Fury, and a 50% chance he'll see both. That's not great!