Say an investigator wishes to use a spell to give him a combat bonus this round and he fails but he also has a Shotgun. Can he immediately stop using the spell to grab his shotgun, or does he need to wait a round while he's hands "burn with random arcane power" as a friend of mine figured before he can swap to his gun?

cartoonsniper said:

Using a spell during combat sticks to your hand even when failed for one round of combat (although a passed spell lasts for all the rounds of one combat).

cartoonsniper said:

Once you've devoted a hand (or hands) to casting a spell, those hands are occupied for that round (that Combat Check). So no, you cannot use a two-handed weapon during the same round you used a hand to cast a spell.

Also note! If you succeed in casting a spell (say, a Wither), the combat bonus the spell provides is only active as long as you KEEP devoting a hand to it every combat round. So you cannot cast a Wither in round 1 and then pick up a Shotgun in round 2 without losing the hand sustaining the Wither (thus losing the +3 it grants).

k, thanks guys

jgt7771 said:

Does this mean you can cast wither, defeat a monster, and fight another monster still using wither?

No: the Wither (or any combat spell) continues to offer its +3 bonus as long as you devote hands to it, for multiple combat checks against the same monster. As soon as you let it out of your hands, say to equip something else, or if the combat ends somehow, the spell de-activates. Note that in final combat, spells are always deactivated and refreshed (except for a couple specific King in Yellow spells) each Upkeep, and so must be re-cast to be used each round.