If you're TB against regulus, sometimes Regulus will get cocky and try to lay mines and snare you. Rain of ice as he approaches, and when he's laying mines, don't attack. you just keep charging him, and then use frost nova. Afterward, of course, use deep freeze on him, and by that point he's going to die very soon, or you've killed him. Remember though, pick TB items well, or he won't be very good. (That means, keep your mana regen/mana pool very well stocked)
Edit: If he's not laying mines, then you'll just have to jump him with a frost nova and use rain of ice afterward. Immediately shatter him after. It's all about timing here though. One missed second in a rotation of abilities, and you might lose a shatter multiplier.