Illusions is the ability of vampires, hybrids, witches and immortals to project extremely realistic illusions into the minds of others by altering the perceptions of reality conceived from sensory distortions be it accidental or forcible.
For the majority of the fourth season Silas has used the ability to further his agenda. He has manipulated thousands of curious visitors, who came to his place of burial, into giving up their blood, so that he could remain active for the duration of his entrapment. He did this by casting illusions of the visitors' dearly departed in exchange for their blood. Later he manipulated Shane by projecting illusions of his wife to arrange for his release. He manipulated Bonnie into completing the expression triangle and dropping of The Veil to the The Other Side, all the way making appearances as different people until he was turned to stone.
Witches have shown different versions of the ability, from implanting images in peoples' minds, to creating a seemingly infinite graveyard.
Immortals have been shown to do a variety of things with their powers of illusions.
- Stimuli manipulations: Silas is able to cast strong realistic illusions that can plague the various senses of his victims. His illusions are a combination of visual, auditory and tactile.
- Shapeshifting: There is no physical shapeshifting involved. Silas merely gets into people's heads and makes them believe they're seeing someone in front of them. He can do this while being physically away from the victim and can use it to his advantage by casting illusions of speedy movements, enough to baffle vampires. In some cases he is physically present and hides himself from view using illusions.
- Voice mimicking: Silas uses his powers of illusion for voice mimicking the person he has into for further convincing his victims.
- Complete visual manipulations: Silas can cast illusions of natural phenomena like wind. He did this when he wanted to convince Bonnie to help him while in the guise of Shane.
- Tactile simulation: Silas' illusions have a tactile feeling which further convinces his victims what they see is real.
- Other sense manipulations: Silas can manipulate various internal senses like the sense of pain and suffocation. He was able to make Klaus writhe in pain after making him believe he was staked. He made Caroline believe she was dead. He made Bonnie believe that the air had thinned around her.
There are quite a few instances where it can be seen that vampires too possess a far lower degree of the ability to cast illusions. For most vampires this ability is present in the form of dream manipulations. Damon and Katherine have been able to cast dreams into unsuspecting victims. Damon has cast dreams on Stefan, Rose and Elena while Katherine has done the same to Stefan. A far more powerful form of the same ability was seen by Lexi , who could in a way, mimic the effects of quick passage of time on Stefan much like Silas mimicked the pain of being stabbed by the white oak stake on Klaus.
Elijah and Klaus have both shown the ability to project images into the minds of others.
New Orleans Witches
During the attempt to sacrifice Hope, Genevieve, Abigail and Monique cast a powerful illusion that essentially created an infinite graveyard. While within it, Klaus and Elijah were able to feel the graveyard as if it were actually there and believed that they were running for miles.
Esther could make people see images that were actually not there. She later used the ability to send a projection of Elijah to Klaus, to try to convince him to take Esther's deal.
Gemini witches are talented in cloaking, a sub-section of casting illusions. Many of the coven's members are known to practice such spells, as seen various times. The leader of the coven, Joshua Parker, kept his entire house under an invisibility spell, making the entire place look like an empty field to strangers. Malachai Parker, the last leader of the coven was able to create various illusions, such as making Elena look like him (achieved by Siphoning the magic from The Travelers' last spell). The Heretics were also skilled in invisibility spells. This power was typically evoked through the Latin-based term "Invisique".
- For vampires, it is an extension of their tactile Telepathy, allowing them to enter minds similar to their ability of Dream Manipulation. However, this is done on a victim which is conscious.
- Their ability to enters other mind is dependent on whether said mind is weaker or willing, older vampires use this skill more effectively, implying that mental strength too, like their physical strength and speed, also grows and evolves with age.