Whilst their early works are hardcore/metalcore, their first album True Nature Unfolds has a strong sludge metal and doom influence.
The band's sophomore album Noir, released in 2006, still drawing from modern sludge also introduced subtle jazz leanings, heavy use of mellotron and experimentation with unconventional rock instruments such as the saxophone and the flute.
The songs on "Providence" are built upon layers of melodies, using a broader palette they have coloured their sound with twangy guitars, mellotrons, prog rock overtones and a singing style that can be traced back to 90s-era vocalists like Layne Stayley.
Secret Youth is a contradictory concoction of more straightforward elements mixed with a strong and somber experimental overtone, or "progressive noise rock" as the band themselves have described it.
In March 2007 Callisto showcased in Canada and the United States, playing at the Canadian Music Week in Toronto and the South by Southwest festival in Austin, Texas.