You probably did the same mistake as I.
After getting Valerie in the team, head south to the woods where you'll be able to find the 2nd temple and a boss fight to prgross the story.
Once done with it, head to the fay forest up north, again to do a boss fight and get the key to the manor (their is additional content in those woods if you talk to the fairies)
then, head to the manor, to the far east of the map, cross the brigde and go up and you'll find it.
complete the manor that you can now open, and when done so, you can go to the beach near the first woods, and use the crystal droped by Lilith in the manor to access the demon nurserie.
When you finish all of that, head to the camp near the volcano, talk to Blake, and the access to the volcano will be open.
Afterwards it should be self-explanatory. If you struggle with what comes after the whole Lakeview quest, ask away and I'll try to detail the rest of the game.