Many of the latest expansions have seen cards to improve your hero power. Some decks are built to synergize with your specific hero power.
Here’s an idea for a tech card you might want to include in a deck to mess up those plans.
Corrupted Sir Finley:
2 mana, 1/3
Battlecry: Discover a new basic Hero Power for your opponent
The stats vs mana cost are sufficiently underwhelming that it’s not going to be a standard card in every deck. But if the meta has lots of decks that improve a players Hero Power (Galakrond, Hero cards, etc), then running a copy of Corrupted Sir Finley would be a good way to counter those decks. It would become popular, until the Hero Power-improving decks become less popular again, at which point this card would also lose value again.