Some cell have several nuclei within their cytoplasm. considering the events in a typical cycle, which phase is not operating when such cells form? i

The second and last phase which is cytokinesis is missing in the cell cycle.

A cell division into two daughter cell involves two phases:

Karyokinesis: The division of the cell nucleus. It further involves many steps like prophase interphase metaphase etc. After this phase cell contains two daughter nuclei.

Cytokinesis: This the division of the cytoplasm of the cell and having the formation of a cell membrane in the middle of the cell separating two daughter nuclei into two distinct cells.

If karyokinesis proceeds but cytokinesis does not proceed. It leads to the multinucleated cell.