I have just killed irenicus, and then sendt to hell or somewhere with the rest of my party, i am now stuck in a cave, with a black dragon, wich i killed.
But now, when i try to leave i can´t, and i get a message that i need to find, tears of bhaal to go further...
Where are they, How do i get them? Please help...

Well since you killed the dragon he must have dropped it when you killed him. Go look around the floor and see if it is there. He would have just handed it over to you if you did not kill him. All the tests allow you to get a tear to place in the door. Then get ready for the finale fight.

That's right. In the room with the door which you can't open without the tears are five stairs. Each of these leads to a 'test', like the one with the dragon. Each test is rewarded with a tear, regardless of how you preform in it. Each tear can be set in the main door by your main character, and each will give your character a bonus, depending on how you preformed in the tests.

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The last arrow of Legolas kindled in the air as it flew,
and plunged burning into the heart of a great wolf-chieftain.
All the others fled. -J.R.R. Tolkien, The Lord of the Rings