There's 3 quests in magincia, from the yellow guy by the gate. Each quest returns a new piece of rubble (all unique, 4 different ones per quest) that require the threads gatherable from either the souls on the island, or leftover from Moonglow. In the case of the Mag souls, the threads will drop in your pack.
1 type requires spirit speaking (can work even at 0 skill, just takes a lot of attempts) to free the yellow mobs. Life threads
1 type (the grey ones) can be killed, but are fast suckers. The can also be exorcised by a necro with that spell (and are several times more likely to drop a thread from exorcism). Thought threads
The last type are red souls (highly aggressive, and call each other for help to dogpile you), and are killed for the thread drops (melee will drop them faster than spells, pets or archery) Fate Threads
The more quests are done, the more the city ruins clean up (and cause less lag). In fact, almost all the rubble on the ground of the city is gone already.
the city can also be invaded, from faction sigil monkey business, which means there might also be some invaders, if not a crimson dragon, running loose as well.
You can repeat sicarii for more poison sacs and gossamers.
The Skeletal liches in the graveyards have an Undead slayer variant of the Tome of Lost Knowledge spellbook (from Treasures of Tokuno) as loot, as well as an Undead slayer version of the Primer Talisman (library talisman). both are loot on the corpse.
The invasion spawns have some sick weapons and spellbooks, especially the generals. these items drop into your pack. I got a spellbook from a general that had 5 DCI, 5 LMC and 29 SDI, and something else I can't remember off the top of my head. Crossbow Generals have normal or heavy crossbows with over 50% DI and 50% SSI, as well as a high HLD value and hit lightning, and so on.
Crimson dragons are said to drop crimson cinctures as loot, but that is the one thing I can't confirm - besides their instanced corpse loot, they also have an explosion loot across the ground of gold and gems, including the alternate form gems that the "strangers" dropped a few months ago.
The hard part is to decide which thing to do.
