A cable TV series about a goblin under the spell of eternal life opened at the top of a chart measuring TV shows' popularity, data showed Tuesday.

"Guardian: The Lonely and Great God" scored 302.8 points on the Content Power Index (CPI) during the week of Nov. 28-Dec. 4 to dethrone the mermaid romance "Legend of the Blue Sea," according to entertainment company CJ E&M and media ratings agency Nielsen Korea.

A scene from "Guardian" (tvN)

The two companies developed the index to measure popularity based on the number of views of related news stories, keyword searches and mentions on social media.

The Friday-Saturday series on cable channel tvN created a stir even before its premiere because it brings together the writer and director of megahit TV series "Descendants of the Sun."

Screenwriter Kim Eun-sook went beyond the limits of her trademark romance material to create an exciting fantasy brimming with state-of-the-art computer graphics and cinematography under the direction of Lee Eung-bok.

Gong Yoo and Kim Go-eun add to the series' appeal with their charming portrayals of the immortal goblin and a high school girl destined to be his bride.

A scene from "Guardian" (tvN)

Four episodes in, the drama has recorded viewership ratings of 6.9 percent, 8.3 percent, 12.7 percent and 12.3 percent, respectively.

In second place, SBS TV's "Legend of the Blue Sea" scored 256 points, trailed by the MBC singing competition show "The King of Mask Singer" with 236.7 points and the SBS medical series "Dr. Romantic" with 223.9 points.

"Legend" tracks the adventures of a mermaid who travels through time and space in search of her former love. Despite a star-studded cast that includes Jun Ji-hyun and Lee Min-ho, and its famed writer Park Ji-eun, the drama has faced criticism that it lacks originality.

Park wrote the hit drama "My Love from the Star," in which Jun played a top actress. (Yonhap)