Yes, in the game Witcher 3, there are only five usable signs. But in the Witcher Universe, there are two other signs, Somm and Heliotrope. Somm is a sign in the books that puts the affected to sleep and makes them open to suggestions. Heliotrope is a sign which protects the Witcher against Magical and Physical attacks. In the Witcher 2, Heliotrope is supposed to be the ultimate Sign but does not make an appearance in The Witcher 3. CD Projekt Red did this because Axii did most of what Somm could do, and Quenn covered all the bases for Heliotrope.