if deities are merely creations of mind,how can there be purelands?
Deities are not completely creations of one meditator's mind. Meditator receives instructions from his/her teacher about how the deity looks, based on traditional description - so in some sense the deity exists in those descriptions and in the minds and stories of meditators passing the idea of the deity on, from generation to generation. So in a certain sense the deity exists over the lifetimes of many meditators who carry it on. And in some sense the character of the deity, the mood or style of the deity (as it's described and is then visualized) is an active force that conditions the meditator's mind.
So in a certain sense the deity actually has independent existence and plays an active role. It's not just meditator's imagination. Once you get seriously in touch with a traditional deity cultivated by thousands of meditator's over the course of many centuries you may realize that this imaginary entity nevertheless has power far beyond your own.
Now, to get to the purelands. The reality we perceive - the world we find ourselves in - is a result of our interpretation. Our reference point, our imprints, our selective attention, our associations, and our mental cycling - are the ingredients our world is assembled from. Correspondingly there are infinitely many worlds we can find ourselves in, some drastically different from a world of an average human.
These worlds can be dark&amp;troublesome or high&amp;pure, depending on the mind of a sentient being assembling that world. Sentient beings sharing a common mindset create a common world they can share.
Purelands exist as a continuum of worlds in the total range of assemblable worlds. So I see nothing strange in the fact that experienced meditators of the past visited other worlds, or were guided by deities helping them visit their world.
Perceiving our world as the only reality, and assuming that our own existence is more substantial than existence of deities is only a habit we are unwittingly cycling in.