The towers have to be destroyed in order in the corresponding lane (i.e. you can't kill the middle tower if the front most one is still alive), characters can teleport to the towers using an item and enemies can destroy the tower for a gold boost, but you are able to destroy your own tower when it is below 150 HP to prevent the opponent from getting such a large boost. A single character can get up to 500 gold for a tower kill, but if it is denied, then he will only gain 100 gold.