1st Edition AD&D Books:

http://archmagev.com/1st_Ed/Rulebooks/
This message was last edited by the GM at 16:00, Thu 07 Apr 2016.

It lasts for one combat round / level.  You must rest for an equal number of rounds to recover.  During that recovery period, you are -10 for all activities.

Clerics have a distinct advantage over mages in that they can pray for spells of higher level.  It will take a full 10 minutes for a divination.  The effects of two clerics casting divination could well be different; it's not simply success/failure.  If it works, your humble GM will also roll a random secret roll that is open-ended high and modified by your level (+5%/level up to 10th level) and Wisdom (+5%/WIS over 13, so 18 is +25%).

Given the nature of this gaming medium and this particular game, I am not playing components except for VERY special magics.  When you run into those, you will certainly know it.  I do encourage you to be as wonderfully descriptive as you all have been.

Extraplaner energy is directed or channeled in different ways.  For clerical spells, it is likely that there will be some variation in anything that is ritual-based.  Certainly for spells beyond 3rd level, you are calling upon a holy influence to guide your spells.  1st and 2nd level spells are mundane memorization.