
Played through the whole game and did some of the dlc. didn't feel any difference from when i played it on windows a few years ago.

The Dark Souls 2 is great experience on Steam Deck, just need the resolution fix on first start
On first start I experienced black screen instead of game. This needs to be fixed by following:
- switch to desktop mode
- start the game
- in settings set resolution to 1280x800
- quit the game
- return to gamemode

Tried Proton-GE as well, with no results.

Works flawlessly out of the box, no tinkering needed. CryoUtilities + dropping the TDP limit down to 7W allows for 2.5-3h battery life.
Installed CryoUtilities with recommended settings
Roll/Sprint on R4, to be able to run while being able to look around with the right stick.
Setting the TDP Limit to 7W, allows you to get 2.5-3h of battery life (LCD Steam Deck).
No cloud saves, so you'll have to back up the saves manually to play on other devices.
If you're planning to play online and you're up to install mods, install Blue Acolyte from the Nexus Mods page!! It prevents cheaters and hackers from dropping illegal items into your inventory and bricking your save file.

Plays really well out of the box, just keep in mind if you play the game on the deck and PC that you need to transfer saves a other way
Game graphics settings defaults on high so i changed it down to medium for a bit of battery saving, it runs about 10-12 watts
Steam Cloud is not enabled for this game

It works just like any PC running this game.
No 16:10, engine is locked to 60fps, will run at 720p 60fps Max Settings. Docked it will run at 50-60FPS 1440p Max Settings.

Works great on steam deck
The online multiplayer works fine without any problem
This games is perfect for Steam Deck since it runs at 60 fps with every graphics settings set to max ( of course you need to check the battery life ), it has fully controller support and there aren't new bugs or glitches.
About 4 hours battery life at default settings. Fan not really audible at 60 fps.
- 45 fps limit
- 8 Watts TDP limit
Installed DS2Fix for some fixes
- 40fps limit
- 8 Watts TDP limit
solid 3.5 hours of gameplay
Classic dark souls experience, same as on any PC