How does Merlin's ability work and what does 'any time' actually permit?
This is a passive ability, usable any time on your turn, including during your start phase before youdraw a card. But, you may still only cast spells when they are normally permitted to be cast (i.e. during your Main Phase when nothing else is on the storyline other than this ability). Technically, if a Crave Golem were attacking during your Start Phase, Merlin could cast a Dodge Roll then!