The Gatekeeper (episode)

Part 1:

When Clare learns of her mother Niella's legacy, she takes on the role of the Gatekeeper. While she is victorious against Necrolai, she tries and fails to overpower Koragg after he kidnaps Udonna and forces Clare to fight him. Clare is ultimately seized by Necrolai and used to raise the gates to the Underworld.

Part 2:

The gates have been raised and Morticon is set free thanks to a crack made from the Titan Megazord. After Nick saves Clare from Koragg, the Rangers reunite and, with Udonna's power channeled through the Megazord, Morticon is destroyed.