These strange blocks of incense exactly resemble incense of meditation. 

If set alight and meditation and prayer are conducted while the incense of obsession is nearby, its odor and smoke will cause the cleric to become totally confident that his or her spell ability is superior due to the magical incense. The cleric will be completely determined to use his or her spells at every opportunity, typically when not needed or when useless. 

Nonetheless, the cleric will remain obsessed with his or her abilities and spells until all are cast or 24 hours have elapsed.

There are 2-8 pieces of this incense normally, each burning for 1 hour.