This spell stores [[favor]] in [[gems]], depending on the [[QL]] of the gem, and your current amount of favor.
You need at least 7.5 favor to cast vessel but it will only use a min of 5 [[favor]] on casting.
If the gem is less than 10QL, the gem is not filled but the priest loses 5 [[favor]] and can gain channeling skill as usual and the gem loses 3QLin the 5 to 10ql range and random below 5ql.
If the gem is above 10QL, you can still cast Vessel on it starting from 7.5 favor, then use it, and it will lose between 3.5 to 4.5QL, and you can
cast Vessel on it again and again (until it reaches 0 QL of course, in which case it will vanish)