You’ll gain access to Tuchanka when you start the loyalty missions for Mordin or Grunt, which, of course, requires you to recruit Mordin and Grunt. After they’re recruited, completing a few missions should trigger their loyalty missions. This may vary a bit, but you should have access to Tuchanka after completing the mission on Horizon, at the latest.
Talk to Mordin and/or Grunt to start their loyalty missions, then travel to the Krogan DMZ, where you’ll find Tuchanka in the Aralakh system. When you arrive (your party doesn’t matter), you’ll be accosted by some krogan, who demands you speak to their leader. Despite their insistence, you’re under no real obligation to do anything if you don’t care to.
Walk down two corridors to the east and north and you’ll reach the main chamber, where pretty much everything on Tuchanka worth seeing can be found.
When you enter this chamber, immediately turn left to find Ratch, who runs a humble shop. Before you buy anything, note you can talk to Ratch about Tuchanka’s Pyjak problem - space monkeys are generally being a nuisance, and being krogan, they’ve got the most krogan solution you can imagine: blowing the monkeys up with artillery. This starts the assignment [Tuchanka: Killing Pyjaks].
|Heavy Weapon Ammo
|Heavy Damping Gauntlets
|Asymmetric Defense Layer
|M-5 Phalanx Heavy Pistol
You’ll start this assignment by talking to Ratch, after which head down a rubble ramp and make your way to the Chief Scout, where you’ll find a Defense Gun Controls console. Interact with it to start a minigame where you’ll have to shoot encroaching Pyjaks - a very easy minigame, just aim ahead of the Pyjaks as they approach to compensate for the travel time of your missiles. Do a satisfactory job and return to Ratch to complete this assignment and score a discount.
Urz and the Fighting Pit
Near Ratch you’ll find a varren named Urz, which you can pet if you interact with it. More importantly, if you buy some Pyjak Meat from Ratch (you’ll need to complete [Tuchanka: Killing Pyjaks] before he’ll sell this) and interact with Urz, you can feed the reptile-dog, which will follow you around Tuchanka afterwards. Somewhat meaningless on its own, if you head over to the Pit Fight Gambling Station you can bet on match with Urz - either for or against Urz, winning 500 Credits each time you bet correctly. If Urz loses, you’ll have to return to the Normandy, then land on Tuchanka again, giving the varren time to recover. You can save scum credits this way, but given the duration of the fights and the low payout, you’re better off just being frugal.
If you head down the rubble ramp and turn left you’ll find the Chief Scout. You’ll need to talk to him to travel to the site of Mordin’s Loyalty mission, and he’ll also give you the assignment Tuchanka: Old Blood: Missing Scout. Lastly, you can find the Defense Gun Controls near the Chief Scout, which will let you play the Pyjak-shooting minigame for the assignment [Tuchanka: Killing Pyjaks].
Between the Fighting Pit and the Chief Scout you’ll find a ramp leading up to a massive vehicle. Talk to the Mechanic nearby to start the assignment Tuchanka: Combustion Manifold.
To the right of the Mechanic you’ll find a tent, which serves as a hospital of sort. Inside you’ll find Fortack, who is what passes as a doctor as far as krogan go. You can chat with him if you want, but the real draw is his shop. You can gain a discount by completing Grunt’s loyalty mission. While Fortack doesn’t sell much, almost everything he sells is interesting, depending on your build. It’s also tremendously expensive; buying all his wares will set you back 270,00 Credits (22,500 with a discount).
|Assault Rifle Damage
|Heavy Pistol Damage
There’s more to see and do on Tuchanka - including meeting the Urdnot chief (who may be an old friend, if they survived the first game…). That said, everything else mostly boils down to opportunities to earn Paragon/Renegade points, lore, or characters related to the loyalty missions for Mordin and Grunt, which will be discussed on their own pages.