I Made Up Forbidden Spells, and They Actually Worked? - Chapter 209 - : Trouble in the Duchy of Tanya

The world had changed when the System arrived, alongside the Cataclysm that filled the world with monsters. The technology was gone, replaced by classes and skills that allowed the people to fight back. When Devon ended up as a Blacksmith, a class that didn’t grant Intelligence, he had to face the reality, that his old career that he loved - mathematical sociologist - was over. Instead, he had ended up as yet another discarded member of the production class, overshadowed by the existence of the System Shops to the point of total marginalization. But, what if all he needed was to reapply his scientific thinking to the System...

Leon transmigrated and became a lab rat for Hydra. But he ended up awakening the sign-in system.[Ding, sign-in reward: Glint-Glint Fruit(Pika Pika no Mi).]He starts by destroying the Hydra Base.He accumulated some time and got himself another reward![Ding! Get the sign-in reward: Sun Breathing Technique.]

Jiang Bai woke up one day and found with shock that he had transmigrated to a parallel world that is similar to Earth. There, he was granted a cheat system to help him forge the path of a tyrant in this new world. He was now stuck in this parallel world body, the body of a weak and cowardly person. Join Jiang Bai as he rose to the top in this new world!

- Description from Novelupdates

First of all, this is not a story where the cannon fodder chambermaid counterattacks and gives the main wife a beat-down! As a lowly s*ave who had been sold a total of six times, Xiao Hua has long become apathetic to her situation. In her past life, she was a cannon fodder chambermaid who was beaten to death. In this life, she decided to turn over a new leaf and live honestly, yet in the end still ended up being sold off. This prince’s estate seems to have pretty good benefits? She could be released at twenty-five, and they’d arrange a place for her to live under their jurisdiction? They’d even get rid of her s*ave records? Great! That’s great! Xiao Hua thus decided to stay in the Jing Prince Estate and do her job properly. It’s a shame she could never overcome the whims of fate…. The master she serves is a “mute boy”, with several influences above him watching like tigers eyeing their prey. To say she doesn’t want to be pampered is definitely a lie. This is the road to survival of a “discreet girl” who clings on to her master’s leg and is solely pampered, yet feels that he never pampers her. The road from a cannon fodder chambermaid to a beloved imperial consort is a little long….