You can only gain access to the spell by taking a feat ('Sahir-afiyun') and being a pesh user. Here is the list of spells the feat gives:
1st—lesser confusion, night blindness, pesh vigor, ray of sickening,
remove fear, sleep
2nd—calm emotions, euphoric cloud, slow suf focation
3rd—lesser pesh addiction
5th—pesh addiction, instant suffocation, symbol of sleep
So, as you can see, the spell has a spell level of 2.
This spell is only for a specific kind of caster who has taken a feat to gain access to it. The lack of spell level on that page is deliberate: you CANNOT add the spell to your spellbook normally as it is not part of any class's spell list.
I'm reviving this thread to respond because I googled how Euphoric cloud is so OP as a lvl 2 spell. This thread has inaccurate info in it. Here is the correction
You do *not* need to have a feat to take this spell. It is found in the Advanced Class Guide.
So for any DM's (like myself) that would like it to have a feat prerequisite are SOL.
Safir-Afiyun is from *Pathfinder Player Companion: Black Markets*, and only allows you to add more spell to your spell list, as the list @cliff rice posted.