Yes, Isiphilon is definitely a goth band because most of their albums belong to the Gothic Rock and Ethereal Wave genres, which are among the core subgenres of goth music. Albums like Essence are examples of their goth sound.
Some of the other goth artists that are similar to them are Cocteau Twins, Aenima, and Poetry Of Shadows.
Isiphilon is located in Portugal, Almada, active in 1997 — 1997. You can find more information about Isiphilon on their GothDB band page.