Summoning demons and angels both have risks—one major risk being that the summoned may not like being called, especially if confined in a protective circle for the summoning. A powerful enough being may break free and harm—or kill—the summoner and anyone else around if the protections, whether magical or not such as a brokered deal or offering, are not strong enough.
Shadowhunters generally frown upon summoning angels. Aside from the dangers, it is often considered as a waste of time as they are not compelled to respond and do not like manifesting on Earth. Among the known summoning rituals that claim to summon angels, it is largely unknown, especially among Nephilim, which actually work.
Summoning demons, by comparison, is much easier as they can be compelled to help—many being willing in exchange for demonic desires—and more easily bound and/or controlled. These summoning rituals are usually, but not exclusively, performed by warlocks.
All summoning rituals differ in terms of how they are conducted. Many rituals require a pentagram drawn upon the ground. Others may require an incantation or chant in either Greek or Latin, or in a demon language such as Chthonic or Purgatic. Some may also require a circle of candles, blood, or runes, either demonic or seraphic; others may also require an offering or a piece of the demon to be summoned. The athame is used in some demon-summoning rituals to draw blood or carve lines of magical force.
Demon-summoning rituals vary depending on the demon and the warlock doing the ritual. Some demons need a particular type of summoning ritual, and not all may be known.
The risk of disaster, injury, or death from a misunderstood or misapplied summoning ritual is very high.
A ritual exists to summon the angel Raziel using the Mortal Instruments. A circle of runes is drawn before Lake Lyn; these runes serve as protection and include the name of the summoner. Holding the Mortal Sword and Mortal Cup in either hand, the summoner recites the summoning spell, then throws the Cup into the lake. The process is then repeated with the Sword; as the Sword hits the water a plume of it erupts and the angel rises from the lake. This ritual, however, can only be done effectively once.
A second, alternate ritual also exists wherein two concentric circles are drawn near a large body of water. Protection runes are placed in and around them for the protection of the summoner, though this is inefficient against the angel's powers. The summoner then stands in their center and reads from a spell book to summon Raziel. This carries more risk as without the Mortal Instruments, the angel is more inclined to simply kill the summoner out of spite.
To summon Azazel, a circle of candles is placed on the ground and a pentagram drawn within it. Demonic runes are marked within the pentagram and four summoners stand at the four cardinal points around the circle. A warlock reads a Latin chant from the book Forbidden Rites and the candle flames rise higher until smoke appears and coalesces into Azazel's corporeal form. No electricity can be used during the ritual.
When Sebastian Morgenstern raised Lilith, who had just recently been vanquished on Earth and scattered between worlds, he chose the Seventh Sacred Site, which was known to be a good place to summon big, powerful demons.
For the ritual, he used a blue-white pentagram. He stood at its edge and called to her through a Latin chant; the beginning goes: "Abyssum invoco. Lilith invoco. Mater mea, invoco..." He put his blood into the Infernal Cup and threw it into the pentagram. A spinning ball of fire appeared in the center of the pentagram that started small and grew into the shape of a woman. The flames slowly darkened, leaving behind Lilith whose body looked like ash and lava. This lasted long enough for Lilith and Sebastian to speak, and for Lilith to provide her blood for the Cup, before she left in the form of particles of light and fire. When every bit of her was gone completely, Sebastian broke the continuity of the pentagram by kicked at it.
- In the late 1800s, a group of mundanes summoned the demon Marax, who went onto massacre his summoners.
- In 1878, the warlock Magnus Bane summoned several demons, including Elyaas, Thammuz, and Marbas at Will Herondale's request. The summoning for Marbas involved a standard demon-summoning ritual and a tooth belonging to it.
- In the 1990s, the Shadowhunter Valentine Morgenstern successfully summoned the angel Ithuriel and bound him for years.
- In 2007, Magnus Bane once again summoned Elyaas at the request of a mundane company seeking to use his services.
- In 2007:
- Valentine Morgenstern summoned Raziel. He was ultimately killed by Raziel due to his actions against the angel Ithuriel and his own children.
- Azazel was summoned by Magnus, Simon, Alec, and Isabelle. Azazel was successfully summoned and requested a happy memory from everyone as payment. The demon proved unhelpful when he simply used the opportunity to try and convince them to set him free.
- The summoning ritual for Raziel, without the Mortal Instruments, was started by Magnus, who added protection circles for the summoner, and finished by Simon, who would be safe from Raziel's wrath because of his Mark of Cain. Raziel was successfully summoned and bargained with.
- Sebastian Morgenstern raised Lilith and helped her partially recover from her scattered state.