Time rift

From the Castlevania Wiki, the Castlevania wiki

The time rift (aka time gap) is where all the characters in Castlevania: Judgment are trapped in. In order to escape, one of them must defeat the Time Reaper. This phenomenon does not repect the normal passage of time, and so allows individuals from different time periods to be in it at the same time, such as:

Simon Belmont from a year after Castlevania

Trevor Belmont and Grant Danasty from a time after Castlevania III: Dracula's Curse

Sypha Belnades from a time before Castlevania III: Dracula's Curse

Alucard from a time after Symphony of the Night

Maria Renard from two years before Symphony of the Night (three years after Rondo of Blood)

Shanoa from Castlevania: Order of Ecclesia

Eric Lecarde from ten years before Castlevania: Bloodlines

Dracula and Death from a time after Symphony of the Night

Carmilla and Golem from unknown time periods

Cornell from before Castlevania: Legacy of Darkness

Against certain individuals, the Time Rift has side-effects, in Cornell's case, it locks him in beast form, in Golem's case, it gives him self-awareness, both returned to normal once they left the Time Rift back to their respective time periods.