Mirror Defence is a variant of Defence available on Tyana Pass, Mars. The Tenno must protect two crystals on different planets, connected by a Void tunnel. This mission can only be completed after the Heart of Deimos quest. During the mission, the Tenno will receive instructions from the Lotus, as well as taunts from Tyl Regor.
In Mirror Defence, the Tenno will start on Mars, defending a large red crystal from Arid Grineer attackers. The defence objective is titled "Rania's Crystal", and the silhouette of a person can be seen inside it. The crystal has no shields and does not regenerate health. The Tenno must defend the crystal for 2:30 minutes, and then must exit through a door to a Void tunnel. The Void tunnel is a strange place, melding Grineer and Corpus architecture, warped and suspended in midair, surrounded by the swirling cyan mists of the Void. Broken fragments of the Grineer and Corpus buildings drift nearby. An Orowyrm can sometimes be seen flying in the background. The other end of the Void tunnel leads to an old Corpus Ship near Venus, where a large blue crystal must now be defended from standard Corpus enemies. This defence objective is titled "Belric's Crystal". It must also be defended for 2:30 minutes.
On both defence tiles as well as the Void tunnel, the Tenno will encounter groups of crystal shards floating in groups or lines. If the Tenno collect 50 of these shards (called "Citrine's Remnants" in the HUD), it will heal the current defence objective completely, give it overshields, and summon a "Prismatic Ward" gemstone that functions similarly to Citrine's ability Prismatic Gem.
Once both crystals have been defended for 2:30 minutes, the rotation is complete and the Tenno have a choice to stay or extract. Each rotation involves the Tenno protecting both the Mars crystal and the Venus crystal, in order.
Lotus: "Tenno, the Corpus and Grineer seek to destroy two crystal formations so intertwined with Void energy that a tunnel forever links them. Protect them at all costs."
Lotus: "Tenno, you're here to defend something that defies my own understanding of the Void. These Crystals need you – stop the Grineer and Corpus!"
Mars wave starting
(first wave) Tyl Regor: "Old War, warframe made, crystal caskets. Caskets for who? Belric and Rania. Mighty good genes they had. Yes! Genes for the tubemen. Smash the crystals. Take the genes. Do the science. My tubemen get stronger."
Tyl Regor: "Having a wee kavat nap, Kril? Rodents in your house, Kril. Thieving rodents, make me come to Mars. Do your job for you. Smash the crystal, break the tunnel. No genes for you."
Tyl Regor: "'Belric the bold. Rania the clever. Unleashed the Infested on Deimos forever.' Never liked that rhyme. Garbage rhyme."
Tyl Regor: "Pitter pitter pitter. Rodents snatch crystals from sick sick Deimos. Stashed one on Venus. Stashed one on Mars. Void kissed, tangled up-like crystals. Tubemen! Smash this tunnel, stop the rodents."
Tyl Regor: "Getting tired, Tenno? Getting sleepy. I can go all day and all night. Watch me."
Citrine’s Remnants reminder
Lotus: "As the enemy is eliminated, Citrine's Remnants appear. The Void, manifesting her last wish to protect Belric and Rania."
Lotus: "Collecting a critical mass of Citrine's Remnants will create a Prismatic Ward to these crystals."
Lotus: "Amass Citrine's lost Remnants to manifest her protective power."
Lotus: "Somewhere, Citrine still seeks to protect Belric and Rania. Collect her remnants to fulfil her final wish."
Lotus: "Seek out Citrine's Remnants to protect Belric and Rania's crystals."
Upon completion of Mars wave
Lotus: "Corpus forces are mounting an assault on the Venus crystal. Stop them."
Lotus: "Corpus forces have regrouped. Go."
Lotus: "Trouble on Venus. Get through that Void tunnel."
Venus wave starting
(first wave) Lotus: "Do you know the story of Belric and Rania? Lovers whose guardian warframe tried to save them by encasing them in her crystal. It is their remains, and the connection forged between them, that you are protecting."
Lotus: "These crystals formed on Deimos ages ago. Now they are being exploited by smugglers. Belric and Rania deserve better than that."
Lotus: "When extreme emotions meet pure Void Energy, they can change reality, bend and break the laws of nature. Might this explain the connection between these crystals?"
Lotus: "If either crystal is destroyed, the tunnel, their connection, collapses. Do not let that happen."
Upon starting a new rotation
Tyl Regor: "My tubemen are endless, Tenno. Are you?"
Tyl Regor: "One more trip through the tunnel of love, Tenno."
Tyl Regor: "Tubemen, try again."