Universal Talent Stones are a way to unlock your champions' Talents without having to collect Talent Stones for each individual champion. You can earn Universal Talent Stones by completing daily quests. For more information about daily quests, read this article.
Universal Talent Stones are displayed at the top of your Talent Page. They work just like champion-specific Talent Stones; to learn how to use them, read this article.
Universal Talent Stones DO NOT combine with champion-specific Talent Stones. If you have 8 Lilith Talent Stones and 2 Universal Talent Stones, you will not be able to use them to activate any of Lilith's rank 1 Talents. You must collect either 10 Universal Talent Stones or 10 champion-specific Talent Stones to activate a champion's rank 1 Talents. The same goes for ranks 2 and 3; you must collect 30 or 90 of a single type of Talent Stone in order to activate these Talents.