In addition to AiO Patch, the following may be obtained to improve the experience:
dgVoodoo started as a wrapper around Glide API, which some old games used at the time instead of Direct3D or OpenGL, allowing them to be played on modern hardware, which don't support Glide. The author also developed a wrapper around ancient DirectDraw/Direct3D interfaces. It uses Direct3D 11 as a wrapping output and requires DirectX 10.1 capable graphics card to work and of course Windows Vista or newer.
I've tried it with Drakan and noticed significantly improved performance (at least doubled, depending on the scene). My specs:
CPU: AMD Phenom II X4 920 @ 3,00 Ghz (overclocked from 2,8 GHz)
RAM: 4 GB
GPU: NVIDIA GeForce GTX 750 Ti
GPU driver version: 347.26 iCafe
OS: Windows 8.1
FPS dipping in the 40s is now much rarer occurrence, while it was quite common before. FPS will still drop when there is too much polygons, but just for the record, some random complex scene that rendered at 15 FPS before now renders at 30 FPS, this was also with Fog Distance set to 200% and everything else maxed at resolution 1920x1080.
It also improves compatibility with Desktop Window Manager, which is responsible for compositing desktop using graphics card and can't be turned off since Windows 8. DWM on Windows 8 causes a lot for problems for Drakan; most obvious issue game not going full-screen and running with poor performance, when that is resolved with Microsoft's own compatibility fix, alt-tabbing is painfully slow. Another problem is dedicated server window freezing, which requires another compatibility fix.
dgVoodoo2 resolves all above-mentioned problems with one sweep.
WARNING: dgVoodoo2 isn't perfect. It doesn't perform optimally on all hardware configurations. I've also noticed on my machine that if design warnings or debug messages are enabled under Developer tab in Riot Engine Options, performance in terms of FPS is quite low (around 30).
You can install it by dropping contents of MS folder into Drakan installation directory. Use included configuration utility to remove the watermark (DirectX tab).
dgVoodoo2 Download page
Primary purpose of ALchemy is to restore 3D sound and EAX effects in old games. Another good thing about it is that it lets game play more sounds simultaneously. Without it, max number of sounds that can be played at once seems stuck at 20. When there is a lot of going on, sounds being abruptly aborted is quite audible.
Owners of Creative sound cards can install it along with sound drivers, then, in ALchemy application, Drakan must be manually added to the game list. Should be pretty much self-explanatory.
For users of onboard audio, process is a bit more involved. Basically, you have to install HOAL (Host OpenAL), rename 2 files in system directories, run a license generator, then finally install ALchemy and add Drakan to its game list. I've packaged everything required in a single ZIP along with the instructions. Also note that you will probably have to temporarily disable your antivirus software, because license generator is picked as trojan for some reason. Host OpenAL isn't exactly free software and unfortunately, it's the only way to get decent sound back in such games.
Creative ALchemy & Host OpenAL