Recently I was asked by a reader in Twitter how to add in Shiva in Devi worship , especially in Devi Tantra Sadhana.
Shiva is included in Shakti.Shiva is Jada and Devi is Shakti and only when they are together, they become effective.
Shiva is the Inert principle and Devi is the Driving Force.
This does not mean one is powerless. Shiva and Shakti are like word and meaning, one is not complete without another. Trying to argue one is higher than the other is not the path of the Sadhaka, Practitioner.
Wherever Shiva is present Devi is there and wherever Devi is present Shiva IS.
Therefore, there is no necessity of specially invoking Shiva in Devi Upasna.Shiva is embedded and present Devi Upasna.
For more on this and on Japa,Parayana and signs of Mantras helping spiritual evolution of a Sadhaka, watch the video.