The components needed for Magma Blast are:
 
1) Fairy Wings (Pixie, 1%), 
2) Pulsating Heart (Thrag, 1%), 
3) Eye of a Giant (Cyclops, 15%), 
4) Crocodile Fang (Crocodile 1%) 

When you have the components, take them to the Gnome 
Merchant in the Shallow Jungle for the spell. 

For the spell Knock, take the black cauldron from the night hag 
(you'll need 3000 enc free) to Seher and trade it for the spell.