When can players announce alternative costs during spell casting?

Players can announce alternative costs while choosing options for casting the spell. When a player casts a spell, they need to go through a series of steps that involve paying the spell's mana cost and selecting any additional options related to that spell. This is the proper time to declare and apply any alternative costs, as they are considered part of the spell-casting process.

Alternative costs, such as a reduced mana cost for casting a spell due to conditions specified by a card, must be declared at the moment of casting. This is when the player has the opportunity to decide how to pay for the spell, which includes any alternative costs allowed by the game rules or specific card text. It is essential to do this before the spell is officially placed on the stack, ensuring all players are aware of how the spell was paid for.

Other options presented do not accurately reflect the timing for announcing alternative costs. For instance, stating that alternative costs can be announced only at the end of the turn misunderstands the casting process; they cannot be retroactively applied after a spell has been cast. Similarly, the option referencing mandatory effects does not provide the correct context because announcing costs is specifically part of the spell-casting decision, not something dependent on prior effects. Finally, suggesting that