"Change" transforming a non-potion card into Possession

[bajo]

In my recent game --  #182307794 , turn 17 -- I had a Possession turn, and as chance would have it, my opponent's hand that I got to play had Change in it. I played it onto Farmhands that was also in the hand, and, lo and behold, among the number of cards I was given the option to turn the Farmhands into, there was also the Possession. In other words: I transformed my opponents Farmlands into Possession (which was gained by me). I don't even think there was -- I'm almost sure there wasn't -- a Potion in that hand (not that it should make any difference, IMO).

[Ingix]

What you experienced is correct.

Change reads:

If you have any debt, +$3. Otherwise, trash a card from your hand, and gain a card costing more $ than it. +Debt equal to the difference in $.

Change only cares about the $ (coin) part of both cards' costs, it ignores other cost parts (like Potions here or Debt in other cases). The the $-part of Farmhand's cost is $4 and the $-part of Possession's cost is $6. Since 4 < 6, you can use Change to turn Farmhand into Possession, getting 2 debt as a result.

The same is true for debt costs, but most cards costing debt cost only debt. Since that means the $-part of their cost is $0, you cannot use Change to turn anything into them. Fortune is the one card that comes to mind whose cost has both $ and debt, and so you can Change a Gold into Fortune getting just 2 debt.