I would like to preface that some of the information are major spoilers. So, read at your own risk.
MC and his family:
Wang Wei: The protagonist of the story. I feel like I should not place his name here, but who knows? Maybe someone needs a reminder.
Wu Hong: The mc's wife, which I honestly think he does not deserve; she's too good for him.
Li Jun: The heir of the Li Clan, one of the three clans (Li, Yan, Wang) ruling the Dao Opening Sect. The mc's life and death brother. They used to wear the same diaper when they were young. (That's obviously a joke, but you get the point I'm trying to get at. That's how close they are.)
Yan Liling (Female): The heir of the Yan Clan and a member of the trio with the mc and Li Jun.
Wang Ju (F): The mc's maid and Intelligence Gathering Officer.
Wang Tian: The sect master and the mc's father.
Yu Yan: The sect madame and the mc's mother; she's from the Yu clan–an Emperor Lineage with one Great Emperor.
Wang Chang: The former sect master and the mc's grandfather on his father's side.
Yun Zhaojun: The mc's grandmother on his mother's side.
Yu Yong: The mc's grandfather on his mother's side.
Yan Chao: the mc's Dao Protector.
Heaven Chosens:
Ji Song: The crown prince of the Great Zhou Dynasty and the owner of the second-ranked physique.
Ji Su: Ji Song's older brother
Han Li: Number one Contemporary Sacred Son of the Dao Opening Sect. Has the Number 12 Heavenly Physique.
Lin Fan: The Number One Physique and disciple from the Emperor Enlightening Academy.
Xu Shi: Considered the most beautiful woman in this generation and Lin Fan's wife.
Su Ya (F): The Number Three Physique and from the Yin Moon Palace.
Jian Wushuang: Born with Innate Sword Bone, an acquired physiques on par with the Heavenly Ones. From the Sword Casting Villa.
Daiji: Jian Wushang's wife.
Feng Heng: The number five physique from the Taiyi Profound Gate.
Shi Fuyu: Feng Heng's master in the form of a grandpa hiding inside his body.
Zhen Biyu (F): Number 6 Physique and from the Five Element Balance Palace.
Fang Lijuan (F): From the Divine Dao League.
Liu Meixiu (F): The owner of the Myriad Beast Physique.
Sun Jiaolong: Crown Prince of the Great Wu Dynasty. Likes to collect swords.
Mo Xingyun (F): Owner of the Heaven Devour Physique, an acquired physique. From the Mo Clan, a clan of devil cultivators.
Zhang Xuan: Owner of the Number Seven Physique from the Worshipping Dao Academy.
Huang Yuan: Sponsored by the Loose Immortal Alliance. Remember, he is the one with that powerful item.
Fan Qianhan: The guy's above ex-girlfriend.
Xiao Songxi: A prince from a small Supreme-level Dynasty called Great Ye, so no Great Emperor as a backing.
Huo Fenghuang (F): From the Ancient Aristocratic Clans.
Ao Shen: The only Heaven Chosen of the Demon race. He's the result of Project Atavism.
Tong Ruobing (F): From the Great Talisman City.
Chen Chen: From Origin Weapon Mountain.
Wu Meng: From the Origin Rune Palace
Jingwu Hua (F): An Emperor Offspring from the Golden Crow clan. Slight Spoilers, she lost her Heaven Will Battle and sealed herself before waking up in this generation.
Di Tian: If you catch up to the current chapters and still do not know who he is, you either do not pay attention or have the memory of a donkey, or I failed as a writer. Something tells me it's the former.
Qiao Ning: Di Tian's wife.
Yi Lianxiang: From the Sea Race--the Deep Squid Race, to be specific.
Yu Zhou: From the Soul Race.
Yang Guowei: From the Yang Clan in the sun.
Yin Gen: From the Body Dao Cave. A sealed Heaven Chosen from the past era.
Important characters to remember who may be important later in the story:
Chen Tong: An Eternal Emperor who created the Slaughter Trial
Xu Junyao: I can't say much, but try to remember her. And, stop hating on the poor woman; she has done nothing wrong.
The Flame Emperor and Lou Cheng: Try to remember their names.
Dong Lifen: The Empress of the Great Xia Dynasty during the trial.
Important Member of the Older Generation:
Bai Hai: Headmaster of the Emperor Enlightening Academy.
Old Chu: Supreme Elder of the Heaven Mystery Pavilion.
Ye Lao: sect master of the Origin Pill Dao Sect, and Lou Cheng's master.
Fu Caiyun: Great Elder of the Origin Pill Dao Sect
Wang Wucheng: Wang Wei's ancestor.
These are all I think are important. In Volume 6, many new characters will be introduced, but most will only be important for that volume. Additionally, as the Heaven Will Battle approaches, more and more people will show up.
If you see that I miss an important character, comment below, and I will add them.