Hickory: It is passive but don't expect it to be as effective as actively searching: it takes a much longer time to detect things.

Just remember that a spell trigger is a one-shot thing, so you need to reset it each time it's used. I'm not big, or keen, on sorcerers, so maybe somebody else who is could give you better guidance.

dtgreene: Can you improve the passive effectiveness even further? Would raising the skill to 200 give a better chance of passively detecting illusions? Or is it a waste to raise it above 110?

Does Find Traps work the same way?

Pangaea666: Got to level 11 and had to choose a lot of new spells, filling out some of the lowest levels. Hopefully not made too many clangers yet.

Level 1: Chromatic Orb, Identify, Magic Missile, Shield, Sleep
Level 2: Blur, Detect Invisibility (?), Melf's Acid Arrow, Mirror Image, Web
Level 3: Fireball, Melf's Minute Meteors, Minor Spell Deflection (new, unsure if decent), Protection from Fire
Level 4: Greater Malison, Spirit Armor, Stoneskin
Level 5: Breach, Lower Resistance

The innate ability of Vampiric Touch is pretty wicked. Never tried it before because I simply assumed it was crap, but the PC ended up in the 'ring' in the Coronet, fighting some bloke, and I tried it. Says I drained 28 HP from the victim, but my own HP went from 60 to 116, so double of 28. That's pretty wild stuff! Obviously all those extra HP are temporary, but almost a double (a lucky roll this time tbf) can mean the difference between being alive and dead.

I see Jan has a very high Detect Illusions ability (thief), is this a passive ability, so it will always be on, or does he need to be detecting traps to spot invisible creatures and such?

Pangaea666: Snip...
Btw, is it worth it to put various spell triggers on a sorcerer? You can only choose so few spells after all.