Welcome to the new Witcher 3: Wild Hunt blog! Every post will include my tips on the various boss battles and my strategy for beating them.
Up first, the Royal Griffin.
This will be your first boss battle. By now, you should have a good idea of how the combat system works. You will also have a crossbow given to you by Vesemir, and will have crafted some potions. For the Griffin I recommend using Thunderbolt. This will increase your attack power with your sword.
The Griffin will be flying when you first encounter it. Use your crossbow to shoot it out of the sky. Don't worry if you miss, you get an infinite amount of the basic bolts. Once the Griffin is on the ground, be aware, it has speedy attacks that can kill you quite fast. Cast the spell of Quen first. This will allow you to absorb an initial hit from the Griffin. Also, use the Thunderbolt potion. Once the Griffin is shot out of the sky it will be dazed. Take this opportunity to get some strikes with your sword but don't get greedy. When it's health bar glows red, a strike is iminant so dodge out of the way. You can now time your attacks with the sword or use your crossbow if there is enough distance.
After half of the beasts' health is depleted, it will again take to the sky and attempt to flee. Chase that sucker down either on foot or on horseback. Once you catch up to it near the windmill, again use the crossbow to shoot it down. Then repeat your method of attack like you did the first time, always weary of the power attack that can kill you in only a few swipes. Get behind it if possible, and continue with power attacks from your sword. Don't be discouraged if you die the first few times, your ability to time your attacks will get better with each attempt. Once it's been defeated, don't forget to loot it for crowns and get its head for a trophy. Congrats, you have just defeated the Royal Griffin! Feels soooo gewd.