Voidstrel

Shapechanger. The Voidstrel can use its action to polymorph into a beast form that is less than or equal to its CR. While using this ability the Voidstrel is unable to use its other abilites.

World Egg (1/day). As an action the Voidstrel may target a creature or object within 5ft. that is medium or a smaller size. If the target is a creature then the creature must make a DC12 Dexterity Saving Throw. On a failure the creature is conjured into a pocket dimension in the shape of an egg that forms around it. This egg weighs 1lb regardless of its contents, has 1HP, an AC of 10, and immunity to psychic and poison damage. At the start of the creatures turn they may make a strength saving throw. On a pass the egg breaks and the creature appears in the space the egg occupied or an adjacent space. If an object is targeted the object is conjured into the egg and remains there until the egg is destroyed or the effect is dispelled. 

Magic Resistance. The Voidstrel has advantage on saving throws against spells and other magical effects.

Familiar. The Voidstrel can enter into a contract to serve another creature as a familiar, forming a telepathic bond with its willing master. While the two are bonded, the master can sense what the Voidstrel senses as long as they are within 1 mile of each other. While the Voidstrel is within 10 feet of its master, the master shares the Voidstrel's Magic Resistance trait. If its master violates the terms of the contract, the Voidstrel can end its service as a familiar, ending the telepathic bond.

Talons. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) slashing damage;

Invisibility. The Voidstrel magically turns invisible until it attacks, uses World Egg, or until its concentration ends (as if concentrating on a spell). Any equipment the Voidstrel wears or carries is invisible with it.

Dimensional Rift.  As a bonus action, the Voidstrel can create an invisible and immobile rift within an opening or frame it can see within 5 feet of it, provided that the space is no bigger than 10 feet on any side. The dimensional rift bridges the distance between that space and any point within 30 feet of it that the Voidstrel can see or specify by distance and direction (such as “30 feet straight up”). While next to the rift, the Voidstrel can see through it and is considered to be next to the destination as well, and anything the Voidstrel puts through the rift (including a portion of its body) emerges at the destination. Only the Voidstrel can use the rift, and it lasts until the end of the Voidstrel's next turn.