While a large amount of information can be discovered by reading the helplesson, some things are simply not in there - because Artifact Entertainment didn't just want to give away this kind of valuable information.  Some of this information may or may not be detailed in the helplesson, it is just what I consider to be information that Demise players should be aware of.
 

• Strength affects the amount of damage a character does in physical combat. (So Giants = best fighters)

• Dexterity greatly helps when disarming traps.  Two thieves of the same skill will have different chances of disarming a trap if their dexterities are different.(So Saris = best thieves)

• Thieving ability not only determines a character's ability to disarm traps in boxes & chests, but also the ability to prevent monsters from stealing gold & items.  So you might want to give those new unknown items that look really good to the party's best thief.

• Intelligence & Wisdom affect the power of your spells.  The higher these stats the more damage you will do with offensive spells, and healing spells will also be more effective.(So Elves= best spellcasters)

• For every point of intelligence or wisdom a character has, 5 spell points will be added to the character's spell point total.

• Charisma is required for charm spells, and a higher charisma makes monsters in the dungeon more likely to want to join you.  A higher charisma seems to make it easier to charm a monster.(So Gnomes = best Magi)

• When companions damage or kill a monster, the character who 'owns' the companion receives 25-30% of the experience they would normally receive.

• High constitution gives you bonus HP before reaching MxLv, and also allows you to recover from poison, disease & paralysis more quickly.

• Spell level is half your guild level, rounded up.  Spell level is taken from the highest guild that can cast the spell being cast, and the lowest mana cost(if a spell can be learnt from multiple guilds) will always be used regardless of the active guild at the time the spell is cast.

• Uncursed items with charges can be 'recharged' provided that the object does not disappear after all its charges have been used. i.e. it is not possible to recharge potions, tomes, etc - this only works for weapons or other objects with spell charges.  Sell the object to the store and buy it again, and it will now have a full complement of charges.

• Sashes are cursed because the cast spells that are very powerful in comparison to other items on the level(s) where you can find a particular sash.  The fact that they are a cursed item means that the store will not buy them, and thus they cannot be 'recharged'.  The sash will increase your A/D by the listed amount and can cast the spell that it lists also(as with all other items, make sure it is correctly aligned to your character).

• Any item ALWAYS sells for a greater amount of money when fully identified than at any previous level of identification, EXCEPT if the item is cursed.  More money will be made from fully identifying items before selling them rather than selling them at a low level of identification.

• However, less money is made by identifying companions before selling them.  So only identify companions to find out all information about them.

• Minimise mana costs for resistances(and any other spells you want to cast) by having one character casting the spells on everyone else, then go to the town and replenish spell points before returning to the dungeon to cast any required spells on themself.