You'll need to unlock a couple of upgrades to perform two teleport-assassinations and escape as a raven. First, I recommend the Raven Endurance upgrade to increase the Power of the Raven's duration, making escaping even easier. Next, you'll need the Jotunheim Assassin upgrade, so you can actually perform teleport-assassinations. Finally, you'll want to unlock the Hugr Reaver upgrade to add an additional Hugr bar so you can use two powers consecutively. Additionally, you may want top unlock the Jotunheim Endurance if you are struggling with getting two teleport-assassinations in one use.
Now, with two full hugr bars, head to an area with enemies and use your bird to mark two enemies that are separate from the main group of enemies and have some space from each other. Each teleport-assassination use4s your full stamina bar, so you will need to wait a few seconds before you can perform another teleport-assassination. Use your Power of Jotunheim to teleport-assassinate one of them, and then the other. Immediately after the second teleport-assassination use your Power of Raven to fly away from the area and land in a safe spot.