After proposing a new runecrafting mini game in late January, the Old School RuneScape team has announced that Guardians of the Rift will be added this week on March 23rd.
The mini game (which also has a new trailer) was originally hinted at way back in December 2020 as a possible new training method, but things evolved and eventually ramped up when the team hammered out the lore and description of the mini game that is still emphasizing training Runecraft, but also with escalating challenge. This mode, Guardians of the Rift, centers the Great Guardian who is trying to close the rift, with Rift Guardians that you can keep charged, create more of, and essentially work to protect the Great Guardian.
Throughout the mode, expect other dangers like Abyssal creatures that spawn and attack the Great Guardian. It's a Skilling mini game so you'll have to craft the right Runes and keep all your help full of energy in order to succeed. The Great Guardian needs to be kept powered up in order to continue working to close the rift. There are a couple of different phases to the challenge, with more difficult monsters eventually beginning to spawn.
The community wanted the mode so it was approved and has been undergoing playtesting. Through playtesting, the @JagexHusky posted that this resulted in a recent change. Over the last few weeks, testing "resulted in a very recent change so that you don't have to use your own pure essence to play Guardians of the Rift. I know some people like that mechanic and we did too in theory, but in reality, it just made the gameplay feel clunky and not really all that fun”. This decision has been finalized ahead of the release this week and there will be more info once the mini game is out on Wednesday following the latest update.