I'm building a magick-leaning half-orc assassin/thief and I'm trying to decide whether to invest points in Pick Locks or Cantrip of Unlocking. I leveled up doing the early fetch quests and saved up the character points so I could try out some variations. My character is at level 10 with 10 unspent character points.

My original idea for the character was to get the Stun spell and focus on Melee/Prowl/Backstab for combat, and get Unlocking Cantrip for thievery purposes.

So I was doing some testing, and Unlocking Cantrip really sucks unless I invest in like 8 spells and get my magick aptitude up to ~40, plus it has the disadvantage that it's noisy and sometimes it will cause a guard or a sleeping shopkeeper to attack me. I experimented with buying Unlocking Cantrip and then pumping character points into Willpower, but this wasn't effective.

It also seemed like the Cantrip of Unlocking either works or it doesn't. When using Pick Locks, sometimes you'll have to try several times, but if you get a critical success you can open something. The spell seemed like it was just checking the stats and not rolling. Not sure about this.

So when does Unlocking Cantrip get good, if ever? Is it worth using only on a hardcore mage with high magick apt? Is there any way to quiet it down? Is it affected by prowling?

Now I am thinking I will invest in Pick Locks instead. I already have the Dexterity for it, although it will pull my magick/tech apt in the wrong direction.

Suggestions or comments? Thanks.

Honestly, it's a rather nice spell in circumstances where you can make noise. Dungeons see a lot of use of this spell, as well as sewers, or back rooms where you can get far enough away that nobody can hear you.
Sometimes, it's enough just to back up until other critters (dock workers, shopkeepers) are barely on the screen before you cast it.
Its primary benefit is that, indeed, it either works or it doesn't. You will never jam a lock casting this spell, and from range it can be used (under some circumstances) to unlock doors and windows exterior to a building you're about to pilfer.

I use both. Unlocking Cantrip alone is merely useful, not a great thieving skill. Lockpicking is almost entirely useless unless mastered, or unless you use Fate Points to save yourself some grief from jamming.
There are locks, or barrels sometimes, which are immune to Unlocking Cantrip. I can't guarantee it never works, but you'll cast yourself into unconsciousness trying repeatedly without success on some, so I can guarantee it's not worth it.

I suppose, as a 2 point purchase requiring WP 12, it's more good than bad. That's my opinion. For a mage, it's not a must-have per se, but it sure makes some places easier and saner!

Edit:
Hmm. You aren't playing a mage, though. Not per se. My advice? Max out Lockpicking. Even my 100% magically inclined thief has spent the points to max out lockpicking, and it does make a difference. There's times I won't pick locks when I can cast this spell as an alternative, but Unlocking Cantrip will never be universally applicable. Lockpicking is.

It is very good on a mage (plus it's a requirement for Teleport). In my experience as a mage, it didn't open the lock in 3 1/2 instances: Isle of Despair treasure chest (had to bash it), Zoological society safe (quest), Caladon temple doors (plot-locked) and Ashbury cemetery room (had to return later).

Its primary benefit is that it keeps doors permanently open. If the npcs sleep in the back room at night, robbing them is easy as pie (eating one, not baking one). Also, if you stand far enough, npcs won't notice. Thus, places I can't break into as a pure mage without neutralizing the guards are really rare (Madam Lil's room, Fenwick's office, Caladon police locker, Caladon prison). Going into prowling mode at all helps, but I don't know how levels in a skill affect discovery.

However, it quacks like an exploit and walks like an exploit. Magick indeed can do anything except persuasion, but "lolololol play a caster instead" is a dumb stance. Unlocking cantrip just doesn't feel like honest thievery. If you're going to play a thief, magick-inclined or otherwise, max out lockpicking. WP 9. /nitpick

Its tied to your magic rating.

Of course, the Zoological Society quest can be opened with a Critical Success on lockpicking, easily obtained with a Fate Point. If you can't find a third Heartstone, this is a godsend.
But such bizarre choices don't require any lockpicking skill anyway.
I found a few more locations where it doesn't work. The inventory barrels in the back room of the Wheel Clan's shops simply refuse to open to that spell. Likewise, a secret entrance to Mr. Willoughby's home. (I think this was mentioned in the promotional materials short story, An Unfortunate Affair. How the bugger did that mage get in? Must have lockpicks.) Thanks, I thought that seemed off.

Thanks for the advice, guys. For this character, I'll go with Lockpicking so I can burglarize silently. Stealing stuff from sleeping people is tons of fun, especially for a hated half-orc. Revenge!

My next character will probably be a pure mage, since I haven't played that yet, and I'll be sure to get Unlocking Cantrip and try it out with a high magick apt.

That is awesome. Very, very awesome.