Question: Following up on All the Lights Go Out, did you have Tamoanchan and whatever sun Titan Sol belongs to retaliate against Hati and Skull for eating two of their Avatars? I can't imagine a greater Titan would not react the same way toward fellow Titanspawn killing their Avatars as they would toward a god that would do it.
Actually, no.
Remember, greater Titans - that is, the Titanrealms themselves - are not people. They are places, concepts and gigantic localizations that represent things, but they're not people. Their consciousness, such as it is, is so vague and massively unfocused that they have no concept of things like reciprocation, vengeance or even the existence of much besides themselves; Tamoanchan can't be mad at anyone, because Tamoanchan is so far beyond the realm of emotions that the idea is meaningless. A Titanrealm is the source, creator and constant propagator of whatever concept it embodies, but it doesn't have a personality and does not take direct actions in any way.
Titan Avatars do have personalities and take action, however; if anyone was going to do something about the presumable demise of Sol and Mani, it would be the Avatars, not the realm itself. However, we doubt very strongly that most Avatars would bother.
There's just no reason for them to. It's not like there are strong bonds of love between the Norse Titans and their fellows - Titans aren't very good at love, and even those who do maintain those kinds of attachments certainly don't have them to Mani and Sol, who have no relatives aside from one another and poor confused Hjuki and Bil. Why should they give a damn that some other Titan ate yet some other Titan? It's not their problem. Amatsu-Mikaboshi is not about to have a breakdown because he can't have Mani over for tea anymore.
And remember also that Titan Avatars are often one anothers' greatest rivals; they may all be trying to blow up the gods, but that doesn't mean they don't often have problems or power struggles within their own ranks, too. For most Titan Avatars, the response to someone else killing one of their number is not going to be, "My god, those bastards! Let's go rally the troops to fight in Sol's name!", it's "Oh, shit, Mani is dead? What can I get out of that, and how can I work the situation so that I come out more powerful in the end?" An Avatar disappearing would create a vacuum of power that none of these motherfuckers with Ambition is going to let sit around unfilled, and while they might shore up their own defenses to make sure the same thing doesn't happen to them, they have no reason to go out wolf-hunting. Fewer Avatars in the realm means the rest get the chance to seize more individual power themselves. They're all about that.
The only major thing to worry about, if you're running a Ragnarok chronicle and wondering what to do with Mani and Sol, is the fact that a Titan Avatar truly dying always irrevocably damages the World. If Mani and Sol really and truly die, the parts of the World they represent die with them, which is anything but good for the balance of the universe. If you're running a game that ends in Ragnarok and doesn't need to worry too much about the aftermath, or running a completely Norse-focused game that doesn't worry about the rest of the world, that's probably not too much of an issue - but what about if you're using other pantheons whose worlds aren't slated to end and have no light anymore, or you want to move on to what happens after?
There are a lot of ways to tinker with it; perhaps you decide that, if nobody prevents the prophecy from coming true, those Titans do indeed die and take their concepts with them (Mani, as the representative of the timekeeping aspects of the moon, might cause lunar calendars and cycles to be permanently disrupted or unpredictable, for example). You could also decide that new Titans immediately take their places, thus keeping universal order more or less intact - in fact, personally, I'd probably assign this job to Hati and Skoll themselves, who can continue running across the sky with their bellies full of light just as they've always done, becoming the new Avatars to replace Sol and Mani (who you could even rule are not truly dead, but rather confined in the wolves' bellies indefinitely). You could also go with the idea that the Ragnarok prophecies aren't literal, and say that since prophecies are often cryptic or mean something slightly different than their popular interpretation, the two wolves "devouring" the sun and moon actually means something different that you ensure happens in your game. You could even decide that Hati and Skoll are secretly minions of the gods, or tricked by the gods into their course of action, and that their attack on Mani and Sol allowed those two Avatars to be safely bound in Tartarus. How you want to roll with it really depends on whether or not you want actual Titan Avatar death in your game, and what you want the world to look like afterward.
But as for some kind of Titanrealm-wide retribution program, no, I don't see any reason that would ever happen. Even if Mani and Sol really are dead or permanently gone, and the wolves really did just lunch and run, the rest of the realm probably just doesn't care. They'll invest in wolf repellant just in case and get on with their Titanic lives.