Wrex has one condition for leading the Krogan against the Reapers: cure the genophage. He wants his people to thrive, and he also wants some payback. Salarians invented the genophage and Turians distributed it across the Krogan planet. Now these two races need hardy and indefatigable warriors to defend their homeworlds.
We find Mordin with a Krogan female who is immune. As he brings her back to health, he also develops the cure. Meanwhile, we assist the Turian Primarch in defusing a bomb, and Wrex with a Krogan team that’s discovered a Rachni nest. (Consequences related to the Rachni queen decision on ME1 are relatively insignificant here, a huge disappointment.)
When the cure’s ready, Mordin’ll use the same delivery method the Turians used for the genophage, a monument called The Shroud, to spread the airborne cure across the world.
As we prepare to deliver the cure, a Reaper latches itself onto The Shroud, cutting off our access. The Turians send air support, and the Krogan travel overland with Mordin. It’s not going to be enough, though, to defeat the Reaper.
And then the Krogan remember Kalros, the mother of all Thresher Maws who lives beneath the planet’s surface. Shepard must activate the hammers that call her. (I had forgotten how difficult this moment is. As I gasped with only one health bar I finally remembered to stop fighting and run like hell. Heh, good times.)
Kalros attacks the Reaper in an epic cut scene. Great game making, oh yeah.
The way is now clear, and Mordin can go up the tower and disperse the cure. Ah, dear. So many variations are possible at this moment based on earlier choices in ME2. It’s everything gamers want, all the consequences that can result from our actions, and the final scene is as emotionally powerful as the end of ME1. In every way that Bioware failed with the Rachni result, they exceeded all expectations with the Krogan plot. This is stellar storytelling. Sometimes the genophage is cured, and Shepard genuinely celebrates with the Krogan. Sometimes it isn’t, and Shepard flat out lies to their happy faces. And every time, the wonderful Mordin is dead.