Q: Dear Sage
Does the eldritch blast of a warlock give off a flash of light or other noticeable visual effect?
A: The rules are silent on this issue (just as they are for most magical effects), so it’s up to the DM to determine how obvious the effect of an eldritch blast is.
The Sage recommends that the eldritch blast be easily visible to any onlooker. The precise nature of the visual effect isn’t terribly important, but a warlock should have a very hard time indeed in camouflaging his eldritch blast attack.
About the Author
The Sage is a mammal classified in the bear family, Ursidae, native to central and southern China. Debate continues as to whether he is truly a bear or more related to the raccoon rather than the bear, or perhaps in a family of his own. When not eating bamboo and answering rules questions, he works under the nom de plume of Andy Collins as an RPG developer in Wizards of the Coast R&D, where his development credits include Complete Mage, Dragon Magic, and the Player's Handbook v.3.5. He can be easily recognized by his large, distinctive black patches around the eyes, ears and on his rotund body.