Which of the following rewards is essential for developing a player’s character in Riftbound?

The development of a player's character in Riftbound is significantly influenced by experience points. Experience points serve as a critical measure of a player’s progress and skill development within the game. As players accumulate experience points, they unlock new abilities, level up their characters, and gain access to enhanced traits and skills that can dramatically impact gameplay. This progression is essential for character growth as it allows players to tailor their gameplay experience, making them more effective in combat and strategic metagame situations.

While cards, achievements, and resources all play important roles in the game, they primarily serve supporting functions in the broader context of gameplay. For example, cards are essential for forming a player's strategy and gameplay style, achievements provide a sense of accomplishment and can grant bonuses but are not directly tied to character progression, and resources are necessary for crafting and upgrading but do not influence the character’s level or abilities directly. Hence, experience points stand out as the key element for essential character development in Riftbound.