They knew nothing.
For most inhabitants of the Moonlit World, the old man was simply an eccentric, insane annoyance, mostly tolerated only because of his mastery of the Second Sorcery. Of course, there were accounts, legends, stories about him taking on the Crimson Moon himself, but those contained at best a grain of truth - or so most thought. It was far, far better than to contemplate the alternative. World-ending threats and lone wolves who stood against them were simply beyond the scope of the ambition for most.
Still, the ancient was mostly given a wide berth, for while his claims to the feats he allegedly performed could be dismissed as self-aggrandisement coupled with the distortion of the centuries, the power he wielded was an undeniable truth. Thus, the community of Magi has grudgingly tolerated him, offered titles, generally doing their best to turn his attention towards other things. Sure, he may have been a braggart and a liar, but nobody wanted to step up and call him that to his face, lest he unleash the power and vicious, cruel humor he wielded. It was widely considered more efficient to bear with the short-term nuisance that was the usual attention of the Wizard Marshal - or, if one was feeling particularly brave or suicidal, an appeal to the Vice-Director of the Clock Tower could also shorten the old man's visits.
They knew nothing.
He didn't mind any of this - in fact, he found it rather amusing. At least this way, he could focus on the really important issues and problems, of which comparatively few were aware, even in the supposedly enlightened, ancient Magi community. As if those hidebound, bigoted, inbred idiots in their ivory towers had any idea about just what hid beyond the darkness. Sure, their basic tenets of Magi life, and the professed ultimate goal would have made them good material for induction, but over the centuries, he found that only a precious few were willing and able to look beyond that too-focused field, to involve themselves with issues that were of no immediate benefit to themselves, or their bloodline.
Of course, there were always exceptions - and thus, the old man occasionally gave advice, pointed people towards specific directions, even contemplated taking on apprentices once or twice. After all, while he was powerful, so were his opponents, and he was not conceited enough to think himself invincible or unbeatable just because of defeating Brunestud. If anything, he considered it a valuable lesson.
They knew nothing.
Thus, when not one but three families of Magi searched him out to ask for his help in their project, he listened. He weighed the dangers and benefits of the plan, considered all their ideas behind it - and while it was a rather precarious notion, he decided that the ultimate aim along with the nature of the contest would be enough to merit indulging those risks. So, he again lent his knowledge and power, felt a measure of pride in the three lineages who came up with the system.
The first attempt at performing the ritual was disappointing, a mess of ad hoc treachery, betrayal, and confused spilling of gifted blood.
The second attempt was little better - yet at least it highlighted clearly the shortcomings of the process, the need for more precise rules for the whole ritual.
When the time came for the third occasion of the ritual, he was cautiously optimistic, hoping for an acceptable result, a spirited competition - yet he was sorely disappointed. One of the founding families tampered with the system itself, contaminated the great work somehow. Fortunately, as he believed at that time, the meddling only backfired on the Einzbern themselves, their Servant a mere shadow of the others in power, a being easily destroyed.
They knew nothing. But in fairness, neither did he.
The time for the fourth ritual came, and as the contest raged on, he paid very close attention. There was something off with the system, a lingering, corrupting essence, a dark, malicious influence permeating the whole delicate structure they had labored so hard to create. While the conflict was brutal and merciless, it was to be expected - after all, the people involved were Magi who prepared for this quite extensively. Well, most of them did, at any rate.
Even if he had not known about the problems beforehand, the summoning pulled off by the insane Caster would have been more than enough to warn him about how things went wrong. Surprisingly (and much to his satisfaction) the others involved managed to work well together to put down the arisen threat, thus vindicating the whole procedure, at least to him.
While he was satisfied, and the destruction of Caster's creature was to his satisfaction, the old man decided to wait and observe the remainder of the contest; he was not sure that the faint traces of corruption were a mark of the corrupted spellbook used by the insane Servant.
They still knew nothing. But now, he suspected enough.
The finale of the War was enough to convince him. The blackened avalanche of unearthly mud and fire, the sheer malice emanating from the manifested Grail, the desperate, scrabbling hatred of the entity wanting to be born, to awaken - this was not something that should be left to chance. No, he could already feel the thwarted entity within the structure of the Greater Grail moving, manipulating, gathering its power. The next ritual would not occur on time, at all.
His senses questing for the threads of influence and power linked to the immense, nameless shadow, the old man chuckled with satisfaction. This was exactly the kind of situation that he was supposed to deal with - and unless he was mistaken, it would grant him satisfaction and amusement in about equal measure.
The master of the Kaleidoscope reached out with his power, sorting through the many worlds touched by the shadow, seeking a proper tool against it. When his senses brushed against a world so similar yet vastly different to his own, he grinned. This would be definitely be fun - and unless he missed his guess, an end to a reckoning long due.
After all, names had power, and he knew the identity assumed by the shadow polluting the Grail - and he knew that there were those in that world wreathed in darkness that hunted the shadow's kind relentlessly. The complicated magic circle flared to life, the dimensional coordinates rapidly aligning, as he reached across the fabric of reality, his power closing its hold on the selected tool.
Sure, it was a somewhat tainted, battered, bitter one, yet it was familiar with the shadow, had very close ties to it - and its very nature made it extremely unlikely that it would succumb to the inevitable temptation offered by the tainted Grail. And in case he was mistaken, well, it had enough weaknesses that the old man could destroy it with comparative ease. He considered his options once more, assessing the other, weighing his potential, then he made his decision.
Yes, this will be enough. Sometimes, it is fun to watch the shadows tear each other apart.