#card explainer

It lets you cast a spell for 0 instead of its mana cost once each turn, as long as that spell’s CMC isn’t greater than the number of time counters on As Foretold.

If there’s X in that spell’s mana cost, X is 0. 

If you’re only able to cast that spell because of an alternate cost like flashback or madness or overload, then you can’t use As Foretold’s effect on that spell.

If there are additional cost like sacrificing a creature, paying life, or discarding a card, you still have to pay those costs.

If there are optional costs like Kicker or Buyback, you can still opt for those extra costs but you still have to pay for them. As Foretold only replaces the base mana cost with 0, not those extra costs.

If you’re casting one half of a split card, As Foretold only cares about the CMC of that half of the card.

Yes, you can cast the half of a split card with Aftermath from your graveyard this way.

Yes, you can cast both halves of a split card with Fuse from your hand this way.

Yes, you can cast cards with no mana cost (e.g. Ancestral Visions) this way.

I normally don’t answer questions about silver-bordered cards, but all of Old Fogey’s abilities are real abilities, so I guess I can cover the basics:

Fading 3 causes Old Fogey to enter the battlefield with 3 fade counters on it.

When Old Fogey begins its first turn under your control, it will phase out before cumulative upkeep, echo, or fading can trigger. 

On your second turn, Old Fogey will phase in, then cumulative upkeep and fading will trigger. Cumulative upkeep will put the first age counter on Old Fogey and have you pay 1 for each age counter on it or sacrifice it. Fading will remove a fade counter from it, leaving two. Echo won’t trigger since you’ve controlled Old Fogey since before your previous upkeep began.

On your third turn, Old Fogey will phase out.

On your fourth turn, Old Fogey will phase in, then cumulative upkeep and fading will trigger. Cumulative upkeep will put the second age counter on Old Fogey and have you pay 1 for each age counter on it or sacrifice it. Fading will remove a fade counter from it, leaving one.

On your fifth turn, Old Fogey will phase out.

On your sixth turn, Old Fogey will phase in, then cumulative upkeep and fading will trigger. Cumulative upkeep will put the third age counter on Old Fogey and have you pay 1 for each age counter on it or sacrifice it. Fading will remove a fade counter from it, leaving none.

On your seventh turn, Old Fogey will phase out.

On your eighth turn, Old Fogey will phase in, then cumulative upkeep and fading will trigger. Cumulative upkeep will put the fourth age counter on Old Fogey and have you pay 1 for each age counter on it or sacrifice it. Fading will try to remove a fade counter from it, but since there aren’t any fade counters left, you’ll have to sacrifice it.

Bands with Other is explained in this post.

Protection from Homarids means that Old Fogey can’t be blocked by Homarids, it can’t have any Homarid permanents attached to it, all damage that would be dealt to it by Homarids will be prevented, and it can’t be the target of Homarid spells or abilities.

Snow-covered plainswalk means that when Old Fogey attacks, it can’t be blocked if the defending player controls a single land with both the snow supertype and the plains subtype.

Flanking means that when a creature without flanking blocks Old Fogey, that creature will get -1/-1 until end of turn.

Ok, so...

When Knowledge Pool enters the battlefield, each player exiles the top 3 cards of their library under knowledge pool. Only the nonland cards really matter, but the lands are still exiled.

When a player casts a spell from their hand, Knowledge Pool’s second ability triggers. When the trigger resolves, if that card is still on the stack, Knowledge Pool exiles it and then allows that spell’s controller to cast any other nonland card already exiled by Knowledge Pool. The card that was originally cast is now exiled with Knowledge Pool and can be chosen for the next spell cast from hand.

The type of the card being cast doesn’t matter since Knowledge Pool grants permission to cast the spell when the trigger is resolving. You can cast an instant into Knowledge Pool and get a creature out of it, for example.