Leyline Tyrant allows you to build up red mana quickly, attacking your opponent for 4 damage in the air while doing it. If your opponent finds a removal spell, you can use all of your accumulated red mana to deal the accumulated amount in damage to them.
This could make for an easy win, especially for an aggressive mono-red deck, which can afford to include a couple of 4-mana creatures. If you are flooded with lands and have the Leyline Tyrant on-board, you will be able to convert all of that mana into damage.
There is also an Irencrag Feat spell that can quickly add an extra 3 red mana to Leyline Tyrant's pool, which practically equates to a free Lightning Bolt.