Arcana Skill for LotFP

I've added a few skills to the Specialist's suite of options before, namely adding Music, First Aid and Sailing. They all get used occasionally, Sailing not so much (yet) and I doubt anybody'll take Music unless I leave Orpheus' lyre lying around somewhere. First Aid gets a good workout though, and conveniently doesn't upstage magical healing.

But there's an odd one out in the original nine skills - Architecture.
This never comes up. For one, if someone asks if one part of a structure was built at a different time to another I'll just tell them. For another, I don't write this stuff down until players ask me what the cave walls are made of and I blurt out the first sedimentary rock that comes into my head like an idiot.
And worse, I gave Dwarfs the ability to innately know direction and feel whether they're ascending or descending underground, which means they don't even need their architecture bonus by level.

Hence, replacement.

Thieves using magic scrolls (at a risk of failure) is pretty standard in trad D&D.
I also dislike both the "take a sip to identify the potion" and "skull the potion to see what happens" models of potion identification. People identifying potions wrong though... that has appeal.

Hence, Arcana.

"Oh this is definitely a Scroll of Sidelong Smirk"

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Arcana: This skill is used to identify potions and scrolls and to cast spells from magical devices such as scrolls, wands and staffs. Intelligence modifier applies to identification attempts.
Identification of magical devices takes a turn and is rolled in secret. Success means you have correctly identified the item (but not necessarily its effects). Failure means you have misidentified the object as a random other object of its type.
You can use Arcana to cast spells from magical devices, but it is perilous. If you fail, look up the number you rolled on the Casting Failure table below.

Casting Failure:
6 – Casting fails, no ill effects.
5 – Item charge or scroll wasted.
4 – As 5, and a Chaos Burst is released.
3 – As 4, and the precise opposite of the spell effect occurs.
2 – As 3, and a Summon spell is cast with creature HD equal to spell level.

Spellcasters do not need to use Arcana to cast spells from wands and staves, and can cast from scrolls with no chance of failure if they have previously cast Read Magic on the item.
A spellcaster who has Identify prepared and uncast gains a +2 bonus to Arcana.

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Some corollaries to the above:
 - Identifying items only tells you what they're called (eg. Potion of ESP, Wand of Fireballs) not their effects or whether they're cursed.
 - You only get one try per object, but of course multiple people can have a guess and hopefully argue about it. If two people guess the same thing it's probably correct.
 - You can't use Arcana to identify anything more interesting than your bog standard limited-use magic item. It's useless against cool stuff like LotFP-grade magic player fuckers.
 - Using Arcana to identify an item sets off Explosive Runes and similar magical defenses if present.

If you are wondering how you are supposed to keep track of misidentified potions and scrolls, give scrolls and potions and stuff a tracking number.
What you do is give them the correct tracking number but the wrong name.
So if potion #161 is a Potion of Invisibility they just write down "Potion #161" on their sheet.
When they go to identify it they think it's a Potion of Poison, so they write that down (if they trust themselves, that is).
Later when they're trying to spike the doom wizard's dinner with the poison you go "what number potion was that again?" and laugh when the guy turns invisible.
This is also useful for working out just what the "red potion" a player picked up months ago actually is. Plus if they find the same potion number at a later date they'll know what it is for sure! Look at that player skill coming in useful.

The idea behind the Casting Failure table is that someone with a higher Arcana skill has more chance of success and less bad possibilities if they do fuck up.
Someone with a 3 in 6 Arcana skill has a 50/50 chance of casting correctly and will definitely not accidentally cast random spells or Summon if they fail.
If they've got a 5 in 6 Arcana skill the worst outcome is that nothing happens.

Int modifier applies because LotFP's ability score descriptions are pretty firm on Intelligence representing pre-game knowledge and magical aptitude. That fits the Arcana skill to a T!
Wizards are also likely to start with a better-than-average Arcana score since Intelligence is their main thing.
Anything that increases the usefulness of the mental scores is good, too.

The spellcaster Identify bonus is due to cantrips. In LotFP, Identify requires a lab and some dosh and a day. Having it grant a bonus makes Identify more of a valid option when you're dungeon-crawling the wizard's tower.
Between a +3 intelligence modifier and Identify, an 18 Int wizard can have a 6 in 6 Arcana score.

"Ahhh yes, the Most Efficacious Ritual of Get the Fuck Out of My Office"

WOAH BUT HOW CAN THIEVES BEAT WIZARDS AT KNOWING MAGIC

Thematically it's a bit like Knock and Spider Climb. Wizards can open locks and climb way better than a Specialist, but only a limited number of times per day and they've got to prep it in advance.
The Thief/Rogue/Specialist does it all day long, but imperfectly.
Same with Arcana, a Wizard can use Read Magic or Identify to work out what stuff does way better than a Specialist, but only a limited number of times per day and they've got to prep it in advance.
Doing stuff perfectly a few times per day vs doing stuff imperfectly all day long is THE spellcaster/skillmonkey divide.

Arcana doesn't actually tell you what an item does, mind you. You'll need Read Magic or Identify for that. At least the Specialist can help you work out what's worth identifying properly!

In terms of in-universe justification, Wizards are basically just crazy people who do magic by feel. It's not fancy book learnin', it's scrawling-insane-gibberish-on-the-asylum-walls-in-you-own-faeces learnin'. It's voices-from-beyond-talking-to-you-through-your-dog learnin'.
If you're not quite so insane you might discover that there are disturbing parallels between the writings and works of different wizards, and it's these parallels are what allow the Arcana-focussed Specialist to decipher and use their writings. These Specialists are likely a little bit mad themselves or have just a touch of the Sight.

Alternatively - maybe like in Harry Potter, wizards are just too lazy to learn anything for themselves because magic does everything for them. If you can mumbo-jumbo yourself a perfect answer, why bother learning something you might get wrong?
It's like doing maths in your head when you've got a calculator right there. Sure you could carry your old sofa all the way to the tip by yourself or you could just call up your mate Gavin to come get it in his ute tomorrow. Learn how to read Japanese or use Google Translate. Read fifty books to get an idea of both sides of a debate or just look it up on wikipedia.
Wizards are either super lazy or too caught up in the whole ripping-through-the-skein-of-reality-for-personal-gain thing to spend time learning how to tell a Potion of Flying from a Potion of Oh Fuck My Skin Just Flew Off.