Dragon Emperor

Dragon Emperor (竜帝) is the father of Platinum Dragon Lord in the New World.

Background
It seems the Dragon Emperor has a family of his own. This includes himself being the parent of Platinum Dragon Lord. Alongside his son, he was possibly alive five centuries ago during the era of the Eight Greed Kings back then. It's currently unknown whether he has survived through the extinction of dragons perpetuated by the group of players.

The Rule of Conspiracy Arc
When considering the possible threats that the Argland Council State can pose to the Slane Theocracy, the Slane Cardinals narrow such threat down to only Platinum Dragon Lord apart from the rest of his surviving kind. Among the councilors who are in control of the Argland Council State, Platinum Dragon Lord is the one that the Cardinals are most wary of due to the fact that he happens to be the child of the Dragon Emperor.

Abilities and Powers
The Dragon Emperor is most likely very powerful in his own right as they consider his son to be a big threat to the Theocracy because of him. Since his son could use Wild Magic, it is quite possible that he should be able to also cast it likewise.

Assuming from his position of strength, the author Maruyama had the Dragon Emperor ranked #1 above the other inhabitants in the New World as it was measured by based levels. However, whether he is the strongest or not remains to be seen as not every True Dragon Lord and Zesshi Zetsumei were taken into account in Maruyama's ranking. Nonetheless, his based levels are above the Vampire Lord.

Platinum Dragon Lord
According to the Cardinals from the Theocracy, they classified Platinum Dragon Lord as the Dragon Emperor's son.

Trivia

 * Elder Coffin Dragon Lord refers to Players like Suzuki Satoru as the filth of the Dragon Emperor.