In Cookie Clicker, "One Mind" is an upgrade that unlocks several upgrades which greatly boost your CPS, especially the CPS coming from grandmas. It also allows you to earn several achievements, which boost your CPS indirectly via Milk and Kitten upgrades. Once "One Mind" is purchased, the Grandmapocalypse begins, and the Grandmas are now considered "Awoken". Wrath cookies will appear 33% of the time, and Wrinklers will spawn around your cookie. Wrinklers look spooky and on the surface, they look evil since they each steal 5% of your cookies per second, up to 10 of them siphoning off 50% of all the cookies youd otherwise be making. However, the trick is that wrinklers give back 10% more than all the cookies they stole when you "pop" them by clicking on them three times. Although the bonuses from the grandmother upgrades past One Mind are decent and usually worthwhile, if you want to avoid wrath cookies, you can stop after One Mind. This lets wrinklers form so you can get their overall bonus, but you still only get a few wrath cookies along with the normal golden cookies. Therefore, whether or not to buy One Mind depends on your playstyle. If you are an active player clicking the golden cookies, it might not be worth it. However, if you are going AFK, it is worth it because the wrinklers actually give you more cookies back than they ate.