Mystic Knights of Tir Na Nog

Mystic Knights of Tir Na Nog was a 1998 - 1999 Irish- American fantasy-adventure series that aired on the FOX television network's "FOX Kids" Saturday morning programming block. Loosely based on Irish folklore, it followed the adventures of four super-powered heroes who protect their kingdom from evil forces. The series starred Lochlainn O'Mearrain, Lisa Dwan, Justin Pierre, and Vincent Walsh.

Aideen's Choice (Season 1, Episode 18)
The evil Queen Maeve (Charlotte Bradley) uses a spell to place Deirdre (Dwan) under her control. Deirdre marches to Queen Maeve's castle and is taken prisoner.

Dark Rider (Season 1, Episode 42)
Queen Maeve opens a portal to another world and summons the wizard Kallach, who uses his magical scepter to hypnotize the Knights into joining his Underworld army.