It inhabits subtropical elfin forest edge and shrubbery, often in areas of regular fire disturbance (Seddon et al. 1996). It is typically found in more xeric, stunted habitat growing on nutrient poor sandy soils on ridges, consisting of lichen-covered bushes, ericaceous plants, succulents, bracken ferns, savanna like areas, and taller humid elfin forest (Davis 1986, F. Angulo in litt. 2012, Heynen et al. 2020). The species can also be found along steep wooded ravines, but does not occur in deforested areas (Heynen et al. 2020). In the Nangaritza Valley in Southeastern Ecuador, the species is found in stunted shrubland and páramo-like vegetation, as well as dense foothills and lower montane forests (Freile et al. 2011). It occurs at 1,750 m-1,950 m in the Cordillera de Colán (Seddon et al. 1996), 1,800-2,200 m in the Cordillera del Cóndor, 1,900 m at Abra Patricia (J. Hornbuckle in litt. 1999) and 1,450 m near Jirillo. In the Cordillera de Colán, males favour higher altitudes than females, at least during the dry season, and feed on different plant species (Seddon et al. 1996). In the Cordillera de Colán, 2-3 males were found at altitudes of 550-700 m (Dauphiné et al. 2008).
The preferred nectar-source for males is apparently Brachyotum quinquenerve, and females in the Cordillera de Colán feed mainly from ericaceous plants (Seddon et al. 1996). In Ecuador, plants used for foraging included the small yellow-flowered terrestrial Guzmania gracilior (Bromeliaceae), the larger, green-and-pink-flowered epiphytic G. garciaensis, the epiphytic, fuchsia-flowered Eleanthus ampliflorus (Orchidaceae), an unidentified small epiphytic bromeliad, the stunted tree Macrocarpaea harlingii (Gentianaceae), an epiphytic Cavendishia spp. and a shrubby Macleania spp. (both pink-flowered Ericaceae) (Freile et al. 2011). It is partially insectivorous. Specimens taken in July had active gonads indicative of breeding, but no evidence of breeding was found during surveys in the Cordillera de Colán in August (Seddon et al. 1996).

Heliangelus regalis occurs in northern Peru and south-eastern Ecuador (Graves et al. 2011). It was first recorded in the latter country in the in the Cordillera del Cóndor in 1999, before being found at Yankuam Lodge in the Nangaritza valley, Zamora-Chinchipe province in 2006 (Krabbe and Ahlman 2009), and then known from 6-7 localities in Ecuador (J. Freile in litt. 2012). It is known to occur at the following localities in Peru: above San José de Lourdes in the Cordillera del Cóndor (Fitzpatrick et al. 1979); Duran, Amazonas (Dauphiné et al. 2008); north of the village of San Cristobal in the south Cordillera de Colán, Amazonas (Seddon et al. 1996); Abra Patricia, San Martín (Hornbuckle 1999); Cajamarca; north-east of Jirillo, San Martín (Davis 1986); the río Chipaota valley in the Cordillera Azul, San Martín (Merkord et al. 2009); and the río Pauya valley in the Cordillera Azul, Loreto (Schulenberg et al. 2001). Recent information suggests the species now also occurs in a greater number of localities in the Chachapoyas and Moyobamba areas in Peru and across the Ecuadorian and Peruvian border at the Cordillera del Cóndor (eBird 2021, GBIF.org 2021). The nominate subspecies occurs in the Cordillera del Cóndor and north-east of Jirillo, San Martín, whereas the more striking johnsoni, recently described from specimens collected at Pauya, Loreto, is as yet only known from the Cordillera Azul (Graves et al. 2011).

Conservation Actions Underway
CITES Appendix II, but no other measures are known. The creation of Las Orquídeas Community Protection Area (Freile et al. 2011) protects ideal habitat in the Nangaritza basin (J. Freile in litt. 2012). Likewise the Cerro Plateado Biological Reserve protects similar habitat higher up in the basin (J. Freile in litt. 2012). Survey to locate additional populations have been carried out (F. Angulo in litt. 2012). The species is considered nationally Endangered in Ecuador and Vulnerable in Peru (SERFOR 2018, Freile et al. 2019). Conservation of forested habitats of the Cordillera de Colán and Abra Patricia have been proposed by Angulo et al. (2008), with the Royal Sunangel listed as a priority species for protection in these areas.

Conservation Actions Proposed
Quantify the population size. Research to locate undiscovered populations (Heynen et al. 2020). Assess the current status and extent of suitable habitat. Monitor the population trend (Heynen et al. 2020).
Designate reserves in the southern Cordillera de Colán and Cordillera del Cóndor (Seddon et al. 1996, Schulenberg and Awbrey 1997). Further expand (and effectively protect) Alto Mayo Protected Forest to include the Abra Patricia locality (J. Hornbuckle in litt. 1999).