Rereading the Core Rules, I just noticed (yet another) little rule I seem to have overlooked, so far:
Triggering a card ability from a card already in play requires no resource match, unless otherwise specified by the ability.
Note the bolded part.
I guess this means that using the Action of The Thing Behind You (Summons of the Deep F110) requires a resource match, since it's triggered when card isn't in play:
Action : Pay 2 and return a <Hastur> character to your hand to put The Thing Behind You into play from your hand.
I always thought paying for abilities never required a resource match
So, I played this wrong so far, right?