Hell
noun
The earth prison is a prison down inside the earth. What prison is under the earth? That would be hell.
じごく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
死後地獄に堕ちる事を願って、ありとあらゆる拷問について研究しています。
I study every possible type of torture in hopes of living in Hell after I die.