Demons
Demons – “Demons do not have souls; instead, they are powered by a roiling demon energy, a vitalizing spark that maintains their form in our dimension” (Clare: Shadowhunters).
To summon a demon, one needs to draw a pentagram and say a spell (Shadowhunters: 1.04, 3.05). During the show, Magnus Bane drew a pentagram and said a spell when he summoned the Valak demon (Shadowhunters: 1.04) and Lilith also drew a pentagram and said a spell when she summoned a demon to go after Clary (Shadowhunters: 3.05). Another way to summon a demon is to draw a pentagram and say, “I summon thee” (Shadowhunters: 2.11). For instance, Magnus does this when he summons Azazel (Shadowhunters: 2.11). Additionally, Jonathan Morgenstern summons Lilith by drawing a pentagram in his blood and saying, “Mother” (Shadowhunters: 2.20). Finally, another way to summon a demon is through a medium (Shadowhunters: 3.18). This is shown when, Alec Lightwood summons Asmodeus (Shadowhunters 3.18).
Top: Image of Demons, (Clare: Shadowhunters).
Angels
Angels - According to Sister Cleophas, “Angels are beloved winged celestial beings” (Shadowhunters 2.06). Also, according to Magnus Bane, “angels are higher beings and they communicate through metaphors” (Shadowhunters 2.10).
To summon an angel, one needs to draw a circle on the ground, step into it and say, “Ignus Oram Probat. Eta Proba Mei” (Shadowhunters: 3.05). After this, if the angel hears the person summoning it, the circle will light up and the angel will appear (Shadowhunters: 3.05). During the show, Clary summons Ithuriel in season three, episode five, “Stronger Than Heaven."
Also, when the Mortal Instruments are combined in the waters of Lake Lyn with a drop of blood, they can be used to summon Raziel who would grant the summoner one wish (Shadowhunters: 2.20, 3.08). However, the ritual can only happen once (Shadowhunters: 2.20, 3.08).
Top: Image of Raziel from Shadowhunters, season two, episode twenty, "Beside Still Water," (Shadowhunters Wiki: Raziel).