The Chronoscope raid is base level 6 in heroics, base level 21 in epics, and base level 32 legendary. Doing it at level can be dangerous as the devils are beefy in hit points and fortitude saves. The heroic and epic versions are more of an "introduction to raiding" raid compared to the others, and as such specific roles are not as requires as in other raids. The Legendary version adds several mechanics and it can be quite difficult for the unprepared. The heroic and epic level versions do not have a lockout at any point, but the Legendary version when you open up the Steam Tunnels. This lockout does not mess up people using DDoor to save on travel time, so it is still safe to use.
The heroic and epic version are given by Nolan Gann in the marketplace. The legendary version is given by Future Nolan Gann, who is located just off to the side.
You'll enter on an airship beside the Chronoscope structure. It is all floating above a swirling abyss. Falling off into the abyss is instant death! Your soul stone will be teleported onto the airship you spawned in on, so if you do fall you can be resurrected there.
Head into the Chronoscope and you'll see Nelle Gann, Professor Tremas, Retcon, and Caratrix (the illithid) inside a barrier, and a bunch of random worker NPCs around it. Talk to Nelle Gann, then talk to Professor Tremas to get the short cut scene to happen.
Turns out the workers are devils in disguise! Kill Bazdor and his tieflings, then talk to the wounded Caratrix so he can open the portal again and send up into the past to chase down the devils and stop them from really messing up the timeline. (the portal will be the glowing floor in the middle of the area. click on it and go through)
Through the portal, you appear in the Stormreach Marketplace near the entrance to the steam tunnels and by The Rusty Nail inn. The way into the rest of the marketplace is sealed off by several of The Twelve wizards. In order to lower the barrier you need to talk to Veheer F'nord. To get to Veheer, go into The Rusty Nail, and inside and to the left is a permanent Dimension Door. Going through it brings you to a floating safe zone above the marketplace, and Veheer is there.
This is also the location of another Star Shrine for completing the Star Fragment Frame in order to properly use a Nebula Fragment for specific Perfected Artifacts. This one gives the Orange Shard of Power, and is hiding behind the counter that Valera Aladore and Falquen al Sarrac are standing behind (the weapon and potion/wand vendors).
You'll also notice that the marketplace looks different than usual. It has a complete tent over it (this is what it used to look like a long time ago), and there is a swirling portal in the sky above it.
Veheer can also give you some temporary spell buffs (none on legendary), and the vendors in the inn below can sell flametouched weapons (if you're doing the heroic version and do not have a good way to hurt the devils, flametouched can help you bypass their DR. Compared to most random loot you should have by this point though it's often not worth the plat to purchase). There is also a potion and wand vendor, as well as a rest shrine inside the inn.
Once you've talked to Veheer, head back down through the DDoor on his platform, then out of The Rusty Nail and back into the streets. Delvarrion Iravati (the wizard by the street level barrier to the marketplace) will now allow you to pass. Talk to him and he'll lower the barrier, instantly causing the Bearded Devil and Tieflings on the other side to attack you.
The Marketplace is a battlezone, and the devils here respawn infinitely. There will be Bearded Devils, Tieflings (archers, fighters, and casters), and Red Abishai flying around as well. Killing many of them (40 then 60 ground forces and 8 air forces in heroic and elite) will grant you bonus exp and bonus chests at the end. Usually a few people are tasked to run laps of the marketplace, killing as they respawn, to get those optionals, while the majority will go and continue the plot and fight the first boss.
Note: in legendary, Abishai spells cause you to gain stacks of Sundered Magic Resistance: lowers your MRR by 5 per stack, stacks up to 10 times (will not go into negatives). Furthermore, Abishai will now have a buff called Chromatic Regeneration, which allows them to heal a massive amount of HP every 2 seconds if damaged by any damage type not opposite to their elemental damage.
Throughout the marketplace are also injured soldiers. Rescuing 15 of them (just by clicking on them as they lay on the ground and selecting the dialogue option to revive them. This doesn't cost you resources, so go ahead and revive away) will also grant bonus exp and a bonus chest. Approximately 20 actually spawn. Here is an image of their locations on the map, though not all of those locations always spawn an injured ally (the one under the large bridge leading to the bank doesn't always spawn, for example). I may have missed a few spawn locations.
Two of the injured can spawn inside structures. The one shown in the image below CAN be rescued even though he can't be seen. The other one inside a structure can be targeted but not interacted with.
Those not killing outside will progress the plot and fight a boss. Someone needs to go into the Phoenix Tavern and talk to Tremas there.
He negotiates a task for Nelle Gann's life. Congregate in the Bank of Kundarak just next door to fight Bloodplate, the first boss.
Note: the fallen over mailbox just outside the bank doors is a treasure chest that you can loot!
