Veritaserum

"veritas" L. truth

The most powerful Truth Serum available, this colourless, odourless potion (which looks like plain water) forces the drinker to tell the truth (HBP9)

• A Truth Potion so powerful that three drops would have the drinker spilling his or her innermost secrets.
• Use of this potion is controlled by very strict Ministry guidelines (GF27).
• According to Snape, Veritaserum takes a full moon-cycle to mature when it is being made (OP32). The trustworthiness of this statement may be questioned, since Snape was speaking to Umbridge at the time and may have wished to avoid giving her the potion, but Snape's subtlety is such that even under those circumstances he may have been speaking the truth.
• Discussed during the first class of sixth-year Potions; students who have achieved an N.E.W.T. in Potions should be able to make Veritaserum (HBP9)
• An alert wizard who's good at Potions can protect himself against the use of Veritaserum by keeping some antidote handy

Well that's what this blog is all about - "The Truth!" ;)