[MENTION=83142]Obistahr[/MENTION]; absolutely. No need for further triggers. In fact, I think your example is likely the most common way in which they are used. Re; detect magic. Instantaneous spells such as Create Undead have a one-off magical effect that creates changes, and then the magic is gone, so detect magic won't rat out your skeletons if they were created this way.Hopefully this is all the information you need, and good luck with your encounter; I hope your ambush suprises and terrifies your players!For a deeper consideration; If your undead were in fact commanded by, say, a death cleric, the ability to detect them with Detect Magic might be debatable. Effects created by supernatural abilities may be, according to FAQ, subject to Detect Magic spells, because they are magical in nature. I'd imagine that the question of whether this would work for the command undead supernatural ability should rest on whether the magic that enables command is instantaneous or not. I can certainly see evidence for it having a longer than instantaneous duration; the command spell has a delimited duration, for example.What can I say? I have a lot of time on my hands this afternoon...