Do I need to keep all treasures

Where a switch type appears on a wall is variable, so while the screenshots below circle what the switch looks like, it doesn't mean you can always look at exactly that part of the wall to see it.

Here are the hidden switch types I've seen.

Also, I have found secrets by doing the following:

• Placing torches in sconces
• Removing torches from sconces
• Finding pressure plates on the floors (which have always been very obvious)
• Placing desired item types in alcoves (such as putting a weapon in the alcove outside the room that says "no weapons allowed")
• Slicing tapestries hanging on walls to cut them down and reveal switches behind them.

Party members in the back row cannot attack enemies, unless:

1. They're wielding a melee weapon that's labelled as a "Reach Weapon", e.g one of the spears those skellingtons drop.
2. They're a Rogue with 12 points in the Assassination skill, which lets them attack from the back row.
3. They're not wielding melee weapons, but are using ranged weapons (like rocks, bows & arrows, throwing knives, or spells)

So, in order to make sure all your party members can attack: put spear-shakers or rock-hurlers in the back row, and bare fists or melee weapons in the front.

If you had a character in the back row with a Reach Weapon who still couldn't reach an enemy, then something weird is going on; maybe the enemy was too far away in general? There might be some more mechanics involving Reach Weapons (like maybe a character in the front with a spear can attack at a greater distance than normal) that could be giving you the wrong impression about effective weapon ranges.