The 4 greater bosses you have to beat to enter the Shrine of Winter are the following:

1

Name:

Lost Sinner

Location:

Sinner's Rise, accessible from the Lost Bastille

2

Name:

Old Iron King

Location:

The Iron Keep, accessible from the Earthen Peak, which connects to Huntsman's Copse

3

Name:

Duke's Dear Freja

Location:

Brightstone Cove Tseldora, accessible from the Doors of Pharros which connects to the Shaded Woods

4

Name:

The Rotten

Location:

The Black Gulch, accessible from The Gutter at the bottom of the hole in Majula

(Is this formatting bad? I wanted both the names and locations to be independently spoiler tagged so people have the option to peek at the location without seeing the name of each boss.)

The MagAdjust of this game is just the damage listed that corresponds to the type of spell being cast, i.e. magic for sorceries, dark for hexes, and so forth. You'll notice on staves that some of them have equal magic and dark damage and some of them are weighted more heavily toward one than the other. The same is true for chimes. That helps you know if the item is better for sorceries, hexes, miracles, or a combination of 2 or 3 of them.

As far as what actually goes into the damage itself, it is a combination of the base damage as mentioned above, your INT and/or FAI depending on which school you are casting, and of course any reinforcements (+1 to +10) you've done to your staff/chime. Additionally, if you infuse Faintstone/Darkstone/etc to your staff/chime, you can add even more damage to the type of spell that applies to the type of spell you are trying to cast. That means you can make a staff weighted toward sorceries even more toward sorceries or you can more evenly weight it toward sorceries and hexes.

As far as wearables go, there are pieces of armor/rings that:

• Increase casting speed
• Give extra attunement slots
• Raise your INT and/or FAI by 1-5 points
• Give you more castings at the cost of HP

I don't know of any items that straight up give you raw spell damage like the Oolacile crown did in Dark Souls 1, but the +INT items definitely make a difference.

Ultimately, they've made your catalyst operate a lot more like a "normal" weapon in Dark Souls II. Just look at the damage number for the type of spell you are trying to cast. Also, pay attention to how well they scale for a given stat just like you would for any weapon. If there is an S under the INT picture on the screen for scaling, it will eventually do more damage than a similar staff with an A for scaling even if it started with less base damage.