Hi! New DM here and I''m thinking on a twist for my party that is supposed to hunt down a necromancer, but they have been helping other NPCs instead, you know help a boy in his farm, a widow to recover her dead husband assets (Do I need to said "dead husband" if I state that is a widow?) and those random on the moment quests.

I'm not against that, I love it, it's a sandbox campaign with no rush, but I want to give them a "the world don't wait for you guys".

I want to introduce an NPC to go talk to them, and gave some spicy info about the necromancer, but that new informant is actually the dead body of an friend of the party NPC that the leave behind (and I know they love him), so he has same armor different fave that will crack and reveal once he is dead.

So I would like to give my Warrior player to do an skill check to see if he can recognize the armor, to give that "something is wrong here" roll and start suspicious before the twist.  https://100001****/

For future reference, put a question like this in one of the forums like "Tips and Tactics", "DMs only", or "Rules and Game Mechanics"

That being said, the check here is to notice that something is off, right? That would probably be Insight.

Alternatively, if they are recognizing the make of the armor, that could be something like a Smithing Tools or History check.

Generally, remembering things is covered under Intelligence, while noticing things is covered under Wisdom

History