So I use this weird naming scheme where first-order interaction pertains to cards which cause player interaction on their own (Attacks, stuff like Council Room), second-order interaction pertains to cards which *aren't* interaction cards on their own, but become them when certain cards are in the kingdom (for example, Rocks can be second-order interaction when Swindler or trashing attacks are in the kingdom), and third-order interaction cards are cards that are NOT first- or second-order, but become interaction cards when certain second-order interactions are in the game with the first-order interactions that make them second-order interactions. For example, Militia is first-order interaction, Caravan Guard is second-order interaction when Militia is on the board, Royal Carriage and Coin of the Realm are third-order interaction when Militia and Caravan Guard are on the board (because when someone plays Militia, you can play Caravan Guard from your hand, and call Royal Carriage/Coin of the Realm).

Some cards have multiple orders (Duchess is first-order by playing it, second-order when someone else gives you a Duchy through Swindler or Ambassador).

Now here are the puzzles:

-Find a loop where a card can keep getting in a higher-order of interaction (or show it's impossible).

-Find a fourth-order interaction card that isn't first- to third-order interaction (or show it's impossible).

-Find the highest possible amount of orders a card has without looping (using the same triggers when climbing orders, e.g. playing Possession in a Possession turn).

-The above challenges without using Attacks (or show it's impossible).

-The above challenges without using Possession (or show it's impossible).

-The above challenges without using Possession and Attacks (or show it's impossible).

Now I haven't given a clear definition for interaction cards. I can't give you a definition, but I can give you lots of examples (not exhaustive):

-Events: Raid, Tax.

-Landmarks: any Landmark where you put VP tokens on piles in the set-up. Mountain Pass.

-Projects: Road Network.

-Cards that use Boons/Hexes, as using Boons/Hexes changes what Boons/Hexes other players will get.

-Cards that care about emptying piles like City, Poacher, Tower.

-Trade Route, Embargo.

-All Attacks.

-All cards that directly influence other player's 'game state'.

Not interaction:

-The usual emptying of piles. Emptying of Split piles/Knights/Ruins.

-Obelisk, as it only changes the property of a card.

-Lighthouse (doesn't trigger).

You can only get to another order of interaction through 'triggering events'. When an [X]-order interaction card triggers something else (before having completely resolved it, but cards that say 'after' also count), then that something else is an [X+1]-order interaction card. Like in the aforementioned example, playing Caravan Guard 'triggers' calling Royal Carriage.

[Xth]-order interaction cards played during a Possession turn become [X+1th]-order interaction cards.

If you're not sure about a triggering event or whether something is first-order interaction, use your intuition.