This item gives the ability to cast darkness once per day.
Given his cost, it's better to buy a wand of deeper darkness. It cost less and, at the minimum price, it gives you 41 hours and 40 minutes of supernatural darkness.
Also, what class are you playing?
Wasn't there some sort of magical item (a skull I believe) that you could cast one of a selection of spells and it remained active for something like a year or some such? One of the spells was desecrate but I believe another was darkness. I want to say it was mentioned for necromancer builds when I saw it.
Edit: Darkskull, and it was unhallow not desecrate, oops.
@ElMustacho - A good find, I've never heard of that item. But you're right, it's not very cost effective and a wand would be far better. I'm playing a fetchling investigator (mastermind)/mastery spy. I picked up the fetchling feats so I have the see in darkness ability.
@Skylancer4 - Again, a very good find that I was not aware of! But as with Elmustacho's item, far too expensive for the benefits. Thank you though!
@Reg09 - I imagine my answer to ElMustacho helped to give some clarification, but basically I want to take full advantage of my see in darkness ability.
Thank you all for the responses!
Huh, buy a potion of deeper darkness and "Alchemical Allocation" it. It costs at minimum 750 gp and given your alchemist?(mastermind is a investigator archetype but they share the spell list) level (probably 7) you can drink the same potion up to 3 times per day without expending it. Maybe more depending on your Intelligence score. You can increase that number if you buy some Boro Bead at 4000 gp each, usable once per day.
Ooh, a very nice spell. I'll definitely pick that up. As long as I can afford to use those slots than I can double my potion cost effectiveness
Sorry, investigator is right and I edited my previous post to reflect that!
It's not doubling, it's literally exchanging a 2nd level extract for a drink. As long as you drink that extract first and use the potion later, you never consume the potion.