The Nechisti shrine was an unmarked structure in a sanctuary of the Nechisti Order, dedicated to the Ancestral Spirits. The shrine was where Nechisti monks entered to receive the gift of purification. The shrine was surrounded by a powerful biogenic field, over eight hundred megajoules, and high levels of thoron radiation.
In 2373, Kes inadvertently stepped too close to the shrine and received a severe neuroleptic shock. To save her life, Captain Kathryn Janeway elected to undergo a purification ritual that allowed the Nechisti monks to enter the shrine unharmed. Janeway was eventually told to take Kes back into the shrine and trust the mercy of the Spirits. She did so, and Kes recovered.
The Doctor subsequently learned that the venom of a nesset bite, used in the ritual, altered Janeway's biochemistry to resist the biogenic field. Once he had applied the same treatment to Kes and Janeway took her through the shrine, the mitigated biogenic field acted as a cortical stimulator and reactivated Kes' synaptic pathways. Janeway, meanwhile, was unaffected by the shrine because the iridium ions near the shrine induced a dielectric effect in her skin, offering more protection. (VOY: "Sacred Ground")