AHEM! Dice pools do not refresh until the next TURN, not next action. Therefore, if you're a mage with wired reflexes and you blow your entire spell pool on your first action you won't have any until initiative is rerolled on the next combat turn. Skills are not considered dice pools and refresh after every instance of their use.
Spell defense is like the opposite of casting the spell. The dice allocated can "attack" any spell cast at the targets with the allocated defense, this includes objects which aren't directly on a person. A magician can allocate sorcery and spell pool dice to any number of targets up to their Sorcery skill. Allocating spell defense is a free action and therefore cannot be used before the magician's action. Meaning, if you're surprised and don't already have spell defense activated, tough krill-cookies. Spell pool allocated to spell defense that is NOT used (ie. rolled) may be reallocated on the players next action. If it is used, the caster must wait until the next combat turn for their pool to be refreshed. Sorcery Dice used in spell defense are lost until the next action whence they may be reallocated (assumed to be automatic unless asked otherwise)
Let's use an example. Sparky the cybermage has a really crappy spell pool of 2 (cyberware and brain-damage do that to you) He was a good mage though, so his sorcery is 6. He can sacrifice his spell pool for spell defense. That leaves him with 2 dice to use until his next combat turn. If he instead allocated 2 sorcery dice, he'd have 2 dice to use to resist BETWEEN each action he gets. Meaning, if he gets 3 actions and gets hit with a spell every initiative pass, provided he allocates sorcery dice, he can resist with those two dice every time. However, if he had used spell pool he could only resist once with 2 dice or twice with 1 die each time. Depending on how the GM feels, spell defense, once declared is considered maintained until dropped.
Spells may also be multicast, however, doing so increases the drain target number by 2 per spell beyond the first for ALL spells cast. Sorcery and spell pool are split up according to the spell. At least one Sorcey die must be designated for each separate spell. Therefore, you can only cast a number of spells equal to your sorcery skill per complex action. Of course, casting 6 spells at once will raise your target number to resist drain by 12 and probably fail or do very little as a result of having very few dice.
Don't forget, when casting spells to include vision penalties. The rule of thumb is, if only part of the target is visual then there is a vision penalty. A target that cannot be seen cannot be cast upon. As a basis, in normal ranged combat, an enemy that is fired at (presuming you have a general idea of where the target is) but cannot be seen, adds a +8 target number. However, when using magic, the target must be seen, therefore, there is no blind fire penalty because it is impossible. If only 1 eighth or less of a target for a spell is seen, then a +7 target penalty is applied and every fraction thereof. To simplify you can say:
76-100% = +0
51-75% = +2
25-50% = +4
1-25% = +6
Blind = No target acquired
Other penalties add on as well. Visual penalties never go over +8. It's up to the GM if magic is possible when the visual penalty is +8.
Don't forget, also that spells that are sustained by the magician add a +2 to all their target numbers (save Damage resistance tests, like drain or combat damage)
