Disclaimer: this is a modified version of the horizon walker (Xanathar's guide) and the planejumper (home-brew by Tacitunum) designed for my home-brew campaign, though should be OK to be used for other campaigns.

Astral stalker's are master hunters who's work crosses planar boundaries between the material plane and its echoes. Constant travelling between the planes infuses the ranger with planar magic granting them abilities beyond that of a normal ranger and allowing them to manipulate the boundaries between planes. Their prey tends to be cross planar organisations, aberrant creatures from other realms, the restless dead and many other inter-dimensional entities. Lawful stalker's attempt to eliminate rogue entities that disrupt the order of the planes, whereas chaotic ones use their abilities regardless of the planar discord created in order to hunt down old enemies from beyond the mortal world.

 

*This involves a house rule of being able to occupy spaces occupied by other creatures and objects if they don't occupy the entire space (so a medium creature may share the same space as another medium creature though certain penalties to attacks and extra opportunity attacks also apply)
**I chose perception as the skill as it involves noticing things in time, and it allows the ranger to apply their wisdom modifier, though at you could optionally replace it with another relevant skill (i.e. not persuasion or something similar as there is basically no link) at your GM's decision, though once chosen, this skill shouldn't be swapped back and forth.
***That is to say, the spell may only target you, is cast using a bonus action and teleports you 30ft to an unoccupied space you can see.

Planar jaunt

At 3rd level, you learn misty step. It is always prepared and is a ranger spell for you, but doesn't count against your number of spells known. You can cast it without expending a spell slot a number of times equal to 1+your wisdom modifier (minimum of once) per long rest. This can also be used on other a medium or smaller creatures. If the creature is unwilling, it can be used offensively by making a melee spell attack as an action against creature (you don't then also have to use your bonus action, the jaunt is included as part of the attack action). On a hit you may teleport the creature instead of yourself. This check automatically succeeds if you are in direct contact with the creator like if the creature is grappling you. It may also be used on non-magical objects of size medium or smaller as long as they aren't attached to a surface. Finally, you may perform jaunts on multiple targets at once by expending an extra use/spell slot per extra target. You gain additional ways to use this spell at later levels. You also gain one additional use of this spell at 7th, 11th & 15th level. It can be cast using a spell slot, but only when you have access to 2nd level spell slots (at 5th level).

Shunt

At 7th level when you use planar jaunt, you may jaunt to a demiplane inaccessible to anyone. Doing so requires concentration. The target of the jaunt reappears at the end of your next turn, unless you end the effect early or lose concentration. You can prolong the effect by expending an extra use of planar jaunt. You can optionally cause the demiplane to deal 3d6 force damage to the target of the jaunt.

 

Extended jaunt

At 11th level, your jaunt has improved so that your jaunt allows you to teleport 60ft and may now target large creatures and objects. You may expend an extra use of planar jaunt/spell slot to extend the distance you can teleport even further to 120ft or to a location that you can't see/is occupied (both effects may be used at once by expending 2 extra uses/slots instead of 1), but if you teleport into an occupied space that you can't see or is entirely occupied (such as a solid brick wall 5ft thick) you are forced into the nearest unoccupied space and take 2d10 force damage per 5ft moved, or 1d10 if the space is only partially occupied*. Your jaunt can now also target 2 creatures/objects without expending extra uses/slots as long as neither of them are large. Finally the jaunt can now be used on creatures/objects within 15ft instead of anything you can touch, although offensive jaunts still must have the attack rolled.

 

Rapid jaunt

At 15th level, your jaunt speed increases. You may now jaunt without expending a bonus action (offensive jaunts still require an action to attack). You may also use your reaction to jaunt on other creature's turns. This allows you to give yourself advantage on certain saves against physical effects and effects that deal area of effect damage, or impose disadvantage on an attack against you, as well as causing yourself to become the target of an attack if you succeed on a perception** check contested by the creature's attack roll. If you succeed then the attack targets you instead, though the number isn't rerolled. You may use any of these reactions once the dice has been rolled, but before the results are applied.

Astral walk

At 15th level you cast misty step without expending a spell slot, but the spell must be used as in the spell description, with no modifications or extra options from this class***.