Grinding is a game mechanic where players are required to perform repetitive tasks. Each task earns the player experience points, levels, items or some other in-game benefit. The player will need to repeat the task many times to accumulate enough of the rewards for them to make a difference.
Often, the more you play the game, the more tasks you have to perform to get the same benefit as before. For example, level 1 may require you to perform 5 tasks, but level 2 may require you to perform 10 tasks for the same increase in level. This "ramping up" of the repetitive tasks allows new players to get hooked on the gameplay before it becomes too repetitive and boring. By the time the grind becomes excessive, players have already become addicted to the gameplay and continue playing even though it's not enjoyable anymore.
It should be noted that Grinding is the core mechanic of many games, and some people enjoy it. For those people, this isn't a dark pattern. However, if Grinding is combined with other dark patterns, like
Pay to Skip where you can spend money to skip parts of the grind, then this dark pattern can be amplified.
Another way this can be amplified is by combining it with the
Wait to Play dark pattern. If you need to perform 10 tasks, but you only have enough energy to perform 5, now you have to put the game down and retain some
Endowed Progress. This is a powerful urge to come back to the game later and complete your goal.