Efrén Tiburcio Márquez[1] (February 22, 1973 – December 23, 2019), known under the ring name Mr. Niebla, was a Mexican luchador enmascarado (Spanish for masked professional wrestler) who worked for Consejo Mundial de Lucha Libre (CMLL).

In 2008 he, and Negro Casas created the group known as La Peste Negra (Spanish for "the Black Plague") that also includes El Felino and Bárbaro Cavernario.

Efrén Tiburcio Márquez made his professional wrestling debut on November 11, 1990, working under the Ring name Chamaco Audaz (the Audacious Kid).

[5] In the early 1990s, Mr. Niebla began working for Mexico's largest professional wrestling promotion Consejo Mundial de Lucha Libre (CMLL).

On April 29, 1997, La Ola Azul defeated El Satánico, Emilio Charles Jr. and Rey Bucanero to win the CMLL World Trios Championship, Mr. Niebla's first major title victory.

[11] On March 30, 2001, Mr. Niebla teamed up with Olímpico and Safari to defeat Blue Panther, Fuerza Guerrera and El Signo to win the Mexican National Trios Championship.

Their second defense against Los Infernales was unsuccessful and on June 23, 2002, Mr. Niebla, Olímpico and Safair lost the Mexican National Trios Title.

[12] One week prior, on June 16, Mr. Niebla had teamed up with Atlantis and Black Warrior to regain the CMLL World Trios Title from Dr. Wagner Jr. Blue Panther and Fuerza Guerrera.

[16] Mr. Niebla would successfully turn back the challenges of Universo 2000, Apolo Dantés, Shocker, Rey Bucanero and Tinieblas Jr. over the next 543 days.

[15][16] Around late 2006 to early 2007, Mr. Niebla left CMLL, he would later explain the decision to leave as a desire for him not to "go backward" down the rankings of the promotion, stating that he felt he would get better opportunities elsewhere.

The trio started wearing large afro wigs, painting their faces black and dancing during their entrances and generally worked a less serious style of match than usual, especially for a serious wrestler like Negro Casas.

[21] La Peste Negra's biggest triumph to date is Negro Casas' title win over Místico, earning the group the CMLL World Welterweight Championship .

[23] In early June 2010, CMLL announced that after recuperating in Europe Mr. Niebla was ready to return to the ring, reuniniting La Peste Negra for the first time in several months.

It was later revealed that his body had rejected the implant he had been given during his previous time away from the ring and it had to be replaced, putting him out of action for approximately a month before he was able to wrestle again.

[25] On August 16, 2010, it was announced that the recently returned Mr. Niebla would be one of 14 men putting their mask on the line in a Luchas de Apuestas steel cage match, the main event of the CMLL 77th Anniversary Show.

[28] At the 2012 Homenaje a Dos Leyendas, Mr. Niebla and Atlantis defeated Rush and El Terrible to win the Torneo Nacional de Parejas Increíbles tournament, where rivals teamed together.

[29] In late 2012 the long-dormant rivalry between Mr. Niebla and his former tag team partner Shocker was resumed as the two began to work on opposite sides of a number of matches, with increasing intensity and animosity from both wrestlers.

[33] On February 18, Niebla, El Felino and Negro Casas defeated La Máscara, Rush and Titán to win the Mexican National Trios Championship.

[36] According to the Wrestling Observer Newsletter, Niebla had disappeared on the third night, and was found passed out in his hotel room the following morning, after which he was rushed to a local hospital for the next three days.

NJPW, reportedly furious at the event, made CMLL pay for the hospital bill, leading the promotion to fire Niebla after his return to Mexico.

[39] Niebla returned to CMLL on April 5, 2015, after his suspension,[40] teaming with El Felino and Negro Casas in a six-man tag team match, where they defeated Máximo, Titán and Volador Jr.[37] On April 26, La Peste Negra lost the Mexican National Trios Championship to Los Reyes de la Atlantida (Atlantis, Delta and Guerrero Maya Jr.).

[50] Mr. Niebla publicly acknowledged that he was an alcoholic, stating in a 2018 interview that his drinking problem had cost him a lot over the years in regards to his career and prosperity.