Bloodborne

Story-related and unmissable. Vicar Amelia is typically encountered as the fourth boss in the game, after defeating the Blood-starved Beast (see the "Blood-starved Beast" trophy). She is a large dragon-like enemy that attacks heavily in front of her, so it is recommended that you stay behind her at all costs. She is easy to hit, so use the short one-handed version of your weapon for quick strikes, and make sure that you stay behind her rather than getting greedy with extra hits, because she hits hard.

See the following video guide:

Vicar Amelia - Defeat the beast that once was Vicar Amelia.

This boss and trophy are fairly easy to unlock if you chose to summon the NPC to help you. During the battle Vicar Amelia will aggro on the NPC making it much easier to deal dps.

Simply stay out of range of any of this AOE moves and continue dealing damage.

In no time you will have defeated the boss your trophy should pop! Enjoy!

The Vicar Amelia trophy is awarded for defeating Vicar Amelia, the boss of the Cathedral Ward. She resides in the Grand Cathedral at the top of the hill the Ward is built around and is a pretty tough enemy to take down. Here are some directions on how to reach her and some tips on how to defeat her.

Directions
Starting from the Cathedral Ward lamp, take the left-hand exit out into the Ward. A couple of Healing Church hunters will be patrolling the courtyard. Get past them and head up the right-hand steps one of the hunters came down. If this is your first visit to the area, a gigantic Church guard will come lumbering into view. Take him out or run on past up the stairs to your right. Note: you can close the gate he passes under to avoid confronting him on future visits.

At the top of the steps you reach a locked gate to a large round plaza. The Grand Cathedral looms in the distance across the way. The only way to open the gate is with the Hunter Chief Emblem, which can be purchased from the Bath Messenger in the Hunter’s Dream for 10,000 Blood Echoes. Once through the gate, you’ll see more giant guards patrolling the plaza. The gate on the far side is locked; you can’t get through that way. Instead, cut through an alley to your left, past some more normal-sized Church hunters, and head into the side streets of the Ward.

Be careful here; there are several enemies that camp just out of sight around corners and in the darkness, waiting for you to pass by unawares. A turn in the road is guarded by a sniper and more roaming townsfolk. Past them you’ll find a ladder leading up into one of the towers overlooking the plaza. From here you can drop down onto a roof and back down to the ground. A large set of stairs leads up from the plaza to the Grand Cathedral above. Watch out for more hunters, a sniper, a dog, and another one of those giant guards. You can open up a shortcut back into the plaza by pulling the lever next to the locked gate at the bottom of the steps. An even better shortcut back to the Cathedral Ward lamp can be found down a side street past the lever.

Boss Fight
Once inside the Grand Cathedral, you will enter the main chamber where Vicar Amelia kneels in prayer. As you approach, she’ll transform into a gigantic white beast and attack.

The Vicar is amazingly strong, especially if you’ve reached her fresh off the fight with Father Gascoigne. If the fight proves to be too much, spend time leveling or exploring further areas nearby. The Vicar has a variety of moves leveraging her long arms sweeping back and forth around her, slamming the ground near her feet, and raking the cathedral floor with her claws. A single hit can easily remove a third of your health or more so timely dodging is, as always, key. Like the other beasts you’ve fought, the Vicar can attack in a frenzy, throwing out multiple melee attacks one after another in quick succession. If she pins you down you’ll be dead quick so keep moving.

She has a few special attacks that fortunately aren’t too hard to avoid; she’ll clasp her fists together, raise them high over her head and smash them down, emitting a burst of dark energy in front of her. When you see her spread her arms wide, back up or get under them fast; she’ll smash them together in front of her and crush you in the middle. If you’re far enough away, she’ll leap into the air, like the Cleric Beast and Father Gascoigne, and slam back down to the ground in your direction. If you happen to be near her face, she’ll sometimes lunge forward and maul you with her fangs. Plenty of ways to die here.

Her last move is the true cause for concern. When low on health, the Vicar will back away from you and kneel in prayer, healing herself for several seconds. This can regenerate a quarter of her health or more if you’re not careful. You can attack her while she’s praying but it won’t stop the healing process. The only sure way to stop her is to bring a set of Numbing Mist potions and use them on her as she prays. This will instantly stop the healing process and will cause her to attack instead.

Despite her ferocity, she does have weaknesses. In her left hand she clasps a gold pendant; if you attack this hand, she’ll drop the jewelry and pause to recover. This is a good moment to attack. You can also strike her head, which will cause her to bleed for a moment and real back in shock. Attack during this pause as well. If you get the timing right while striking her head, you can do a special finishing move that will deal massive damage to her.

When not going for one of her weak points, try to dodge between her legs and stay behind her as often as possible. This will keep you out of range of most of her attacks. It can be hard to see clearly when hiding behind or beneath her; her long billowing hair can mask when she’s moving her arms to attack. However, be careful; she’ll turn quickly, and her raking attack with her right hand can reach behind her.

While Molotovs aren’t incredibly useful here, Fire Paper and a decently leveled weapon can do serious damage to her. Try to save any Fire Paper you find and bring it with you; you most likely won’t be able to buy any yet, so it’s a precious commodity. Bring a full set of Blood Vials with you as well; you’ll need every single one.

For those interested in a video of the fight, check out the following from PS4Trophies:
Once you kill her, she will drop her Gold Pendant. Her death also unlocks the Grand Cathedral lamp for your use. The real prize however is the item on the alter that the Vicar was guarding. Upon inspection, it will give you what you need to enter the Forbidden Woods. Congratulations!