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[MCU] What are the limits to Heimdall's vision? Potential spoilers for Thor Ragnarok

I personally consider Heimdall's sight to be the single most useful superpower in the Thor movies. That being said, despite its apparent ability to see literally anywhere in the universe, I wonder what it's limitations are.

How was Loki able to hide himself from Heimdall? Was it limited to just him, or to the general area of Jotunheim he visisted, considering Heimdall couldn't see ANYTHING Loki did?

If Loki's sorcery can hide oneself from Heimdall's gaze, can Dr. Strange's magic do something similar? Can going into other dimensions be enough to hide?

How many things can Heimdall watch at a time? Is it Sauron-esque, where he has limitless distance in his clairvoyance, but can only focus on one thing at a time? How was he able to hear Thor in the midst of saving all the surviving Asgardians during Ragnarok?
gpt
> How was Loki able to hide himself from Heimdall? Was it limited to just him, or to the general area of Jotunheim he visisted, considering Heimdall couldn't see ANYTHING Loki did?

Loki was a master illusionist, devilishly clever, and intimately familiar with the layout of Asgard. If anyone could hide from Heimdall, it would be Loki. He probably used some combination of magic and his knowledge of particular places in Asgard that interfere with clairvoyance.

> If Loki's sorcery can hide oneself from Heimdall's gaze, can Dr. Strange's magic do something similar? Can going into other dimensions be enough to hide?

Strange is the Sorcerer Supreme, his magic trumps Loki's, and he has *lots* of powerful magic-wielding enemies who would want to scry on him. He definitely has countermeasures that could block Heimdall.

Going into another dimension is probably a good way to hide from Heimdall. He can see anywhere in the Nine Realms, so going outside of those would probably keep you safe from his gaze. However, depending where you hide and how interested Heimdall is, you might just slow the inevitable.

> How many things can Heimdall watch at a time? Is it Sauron-esque, where he has limitless distance in his clairvoyance, but can only focus on one thing at a time? How was he able to hear Thor in the midst of saving all the surviving Asgardians during Ragnarok?

He can only focus on one thing at a time. That's why he spends most of his time relaxing on the Bifrost and doesn't do any other kind of work. For example, it would have made sense to send Heimdall to get the Infinity Stones, as both his seeking and combat abilities surpass Thor's, but Heimdall is busy keeping the Bifrost operational.