How does Undying Loyalty cost work? Do you choose the unit you want to play at the moment you play the spell, and pay 2 less if that unit is a cat, dog, poro, or bird? Or do you first pay 2 energy and a power, then choose a unit, then based on the choice get the energy back?

To understand how Undying Loyalty works, we must look at the standard sequence for playing a card (Rule 357 and Rule 356).

The short answer is: You choose the unit first, and the cost reduction is applied before you pay. You do not pay the full cost and get energy back.

Here is the step-by-step sequence for playing Undying Loyalty:

1. Initiate: You place Undying Loyalty on the chain.
2. Make Relevant Choices (Rule 355): You choose the unit in your trash that you intend to play.
3. Determine Total Cost (Rule 356):
   • The base cost of Undying Loyalty is [2] Energy and [1] Power.
   • The ability states: "This costs [2] less if you choose a Bird, Cat, Dog, or Poro."
   • Because you made the choice in Step 2, the game checks the chosen unit. If it is a Bird, Cat, Dog, or Poro, the discount is applied to the total cost immediately.
   • In this case, the [2] Energy cost is reduced by [2], making the total cost to play the spell [0] Energy and [1] Power.
4. Pay Costs (Rule 357): You pay the final calculated cost ([0] Energy and [1] Power).

Key Takeaways:

• No "Refunds": Because the cost is determined and applied before you pay, you never pay the full amount and receive a refund. If you choose a valid unit, you simply pay the discounted price.
• Legality: You must choose a valid target (a unit with cost no more than [2] and no more than [A] in your trash) to initiate the process. If you cannot choose a valid unit, you cannot play the spell.
• Timing: The choice is locked in when the spell is placed on the chain. If the chosen unit were to somehow leave the trash before the spell resolves, the spell would still attempt to resolve, but the target would be invalid (Rule 355.8).