"Alessa" refers to multiple subjects. See Alessa for more uses.
Do you remember how you killed all those seeds of evil for me? For us! Just like you promised, we cleaned this place of the bad things, together.
—Alessa to Karen

Alessa is a character in the mobile phone games Silent Hill: Orphan, Orphan 2 and Silent Hill: Mobile 3. She has no relation or connection to Alessa Gillespie from Silent Hill, though, like Alessa, she is revealed to have split herself into two entities.

Unlike her other similarly named counterparts, Alessa's representation in Silent Hill: Orphan is a much darker character than the misunderstood Alessa Gillespie. Alessa is the voice the characters hear throughout the game. Her purpose in the game is purely for revenge for being put in Sheppard's Orphanage approximately 30 years before the game takes place. Throughout the game she speaks with characters Ben, Moon, and her sister Karen.

Silent Hill: Orphan

Ben and Moon were previous orphans at the orphanage. Throughout their plot she attempts to manipulate them into getting killed. Alessa succeeds, as Ben is killed by an unforeseen force towards the end of his plot. Moon is suicidal and Alessa tries to convince her to kill herself, although Moon resists and tells Alessa to go away. Alessa is revealed to be Karen's sister, and at the same time deceased. Karen learns the truth and realizes that she was the one responsible for slaughtering the majority of the orphanage under the manipulation of Alessa. Towards the end of Karen's plot Alessa becomes hostile and attacks Karen for fear of her turning on her.

Silent Hill: Mobile 3

In Silent Hill: Mobile 3, Alessa returns as a voice heard by the playable characters, Vincent and Emilie. She instructs Emilie to kill herself with a holy knife. Alessa uses Emilie by having her take the spirits of the dead children into herself and freeing them by suicide. This gives more power to Vincent, whom Alessa wishes to use to help her fight Karen. She had thought it would be enough to enlist the help of Lucas to kill Karen in Orphan 2, but part of her survived, leading to the events in Mobile 3. Alessa keeps Vincent alive in order to kill Karen, after which she "sees no reason to keep [him] alive", and he dies. Also it is revealed that in addition to revenge, Alessa murdered the orphans to "wake up" the spirits of monstrous form which Karen faces at the end of Silent Hill: Orphan. To let the spirits free, Alessa needed to "wake up" (kill) all the orphans of the orphanage and thus fulfill a promise she made to her sister Karen, that they would "wash away all the evil and would find a wonderful place to live".