There once were 2 kingdoms. Both kingdoms were separated by a gigantic border. The border was a long, pastel yellow line. Although pastel colours are known to be calming and soft, it instead struck fear and cautiousness. A barrier accompanied the border; stretching up into the white fluffy clouds above. This barrier could've been seen from miles away or even up in space. It had a certain... sparkle to it. Foreigners would think it was beautiful but the locals knew otherwise. These 2 things became known as "the Line of Execution". If anyone were to pass this line, they would be immediately executed, thus the name. Be it royals or peasants, background didn't matter for the Line was merciless.
The kingdom on the South Side of the Line was called "Scelus". The term was coined when the king, Joshua Kaye, failed to get his son married to a suitable maiden. So, he gave it all to his son, Fendrick Kaye. He ended up losing a bet to the other kingdom, causing Scelus to go bankrupt as a result, causing the kingdom's poverty levels to rise immensely.
The kingdom on the North Side of the Line was called "Opulentus". It is completely different from Scelus. Since they won the bet, Opulentus was showered in riches. The king, Quint Clinton, used the money for his people. All his subjects admired his drive for making Opulentus a better kingdom than their now bankrupt neighbour. Scelus couldn't compare to their neighbour; Opulentus had the riches and the resources while Scelus had nothing. This made Scelus less attractive for trading, worsening their already increasing poverty levels.
Quint's subjects would, however, change their perception of him when he added... the border. Quint never told his subjects or even his own son, who was born just before the border was built, why it was implemented. At this point, the king and prince of Scelus have died, leaving the townsfolk to fend for themselves. Quint warned both kingdoms that crossing the border would be an immediate death sentence. Some people were brave enough to step over the border at that time. As they say, "Ask and it shall be delivered." Quint executed the few people that crossed the border with no mercy. The king Opulensians taught they knew went in an instant.
The kingdoms were never the same again.
This happened 2 decades ago.