I want to play a fire elemental against my players.
I need some clarification on the special attack "burn"
A creature with the burn special attack deals fire damage in addition to damage dealt on a successful hit in melee
Do fire damages deal every hit?
(if burn 1d6) as full attack if there is two successful hits and the player don't success the reflex save. the fire damages additionnal is 2d6 or still 1d6.
At the next round if there is a new successful hit, do the fire damages become 3d6 ? and so on ...
or it only applies once.
Burn will apply its damage everytime the creatures hits someone or everytime it is hit by someone (with natural or unarmed attacks). You will check their Reflex save for Catching on Fire every time, but the effects of Catching on Fire will not stack.
Using a medium fire elemental as an example. Every time it swings, it will do its slam damage plus 1d6 fire damage. The creature it hits must make a Reflex save (DC 14) or it catches on fire. At the start of its turn (for the next 1d4 rounds if it doesn't extinguish itself sooner) it will take 1d6 fire damage. It will still take 1d6 fire damage from the Burn ability if the elemental hits it again or if it hits the elemental while on fire.
You will still need to check every time the creature takes Burn damage because, even though he can't be 'caught on fire' twice, you have to roll a 1d4 to see how long he will burn for that particular instance (keep it a secret, the PC shouldn't know). Catching on Fire will not stack, it overlaps. So if a PC Catches on Fire for 2 rounds and the next round they would Catch on Fire again and you roll a 3, they will be on fire for 3 round, not 4 or 5. If you rolled a lower duration, you just use the longer one from before. The Burn target can't be Caught on Fire twice, however, so it will only take the 1d6 fire damage at the start of its round regardless of how many times it's failed its Reflex save (unless it's hit by a creature that does more Burn damage, in which case use the larger amount). It only takes one Reflex save to extinguish the flames, so even if they've failed three times, there's only one fire to put out and doing so extinguishes them completely.
thanks a lot for your answers. It's very clear.
Now, with this special attack the PC's objects can catch on fire too.
I looked at rules on the destruction of object.
I found this table :
"Table: Substance Hardness and Hit Points"
Substance Hardness Hit Points
Glass 1 1/in. of thickness
Paper or cloth 0 2/in. of thickness
Rope 0 2/in. of thickness
Ice 0 3/in. of thickness
Leather or hide 2 5/in. of thickness
Wood 5 10/in. of thickness
Stone 8 15/in. of thickness
Iron or steel 10 30/in. of thickness
Mithral 15 30/in. of thickness
Adamantine 20 40/in. of thickness
The scrolls, Cloak of resistance, the belts which are paper , leather and tissue burn very easily.
"Magic Armor, Shields, and Weapons: Each +1 of enhancement bonus adds 2 to the hardness of armor, a weapon, or a shield, and +10 to the item’s hit points".
Is it also true for the magi objects?
Items don't usually have to make saves against catching fire. The exceptions are if the items are lying around unattended (e.g. on the ground, not being carried or worn), or if the character wearing or carrying them rolls a natural 1 on their saving throw. There's some detail on that here.
The rule about the natural 1 on the saving throw is often ignored, by the way. It's usually seen as unnecessary detail.
Cloaks and belts etc. don't get any extra hit points or hardness.
To affect an item with burn you need to attack the item, not the creature wearing it. Then hardness, halving energy damage and so on enter in play.
As avr said, a lot of magic items don't get extra hit points and hardness, so they are very fragile.
Paizo published the spell Hardening in the past but it was for the 3.5 and wasn't reprint for possible copyright problems.