Although bosses guard essential upgrades and always give massive amounts of XP it is advised that you avoid the temptation of trying to take them on straight away and instead thoroughly explore every room on the level so you gain all the items and XP you need to defeat the boss.
Explore Areas
Explore the different areas in the castle as thoroughly as possible so you can find new items, discover hidden upgrades and fight enough enemies to level Miriam up. The map is full of save points, teleportation rooms and shortcuts to previous areas which you will not find if you do not explore.
Inaccessible Areas
You will come across some areas that will initially be unaccessible and will require the right tools to access them. These include locked doors, gaps that are too far for a human to jump, and platforms that are too high to reach. When you get to these areas make sure you add a marker on the map so you know where to return when you have what is needed to access them.
Level Grinding
The easiest way to level up in Bloodstained: Ritual of the Night is to find a room that is preferably near a save point that houses a horde of XP-rich enemies that you can defeat. Then once you have defeated them, exit and immediately reeter the room to get more XP from them as they will have respawned.
Pay Attention to Doors
You will encounter two types of doors in the game: silver ones with red outlines and black ones that have yellow-orange flame patterns. The silver doors with the red outlines are safe and signify that a new area lies beyond. The doors with the flame patterns however indicate a boss fight is about to happen. Before engaging in this boss fight it is advised that you go back and save, check your equipment, and level up as much as you can. There are also certain doors in Bloodstained: Ritual of the Night that require keys to access them.
Search for Breakable Walls
Everything may not be as it seems when you enter a room that appears to be a dead end. Many rooms will have valuable items hidden behind breakeable walls. Identifying these breakable walls is not easy as they look identical to their sturdier counterparts and the only way you will be able to tell if it is breakeable is by hitting it with any weapon you have equipped. If a wall begins to crack you can be sure it is hiding a secret.
Study Enemy Patterns
The enemies in Bloodstained: Ritual of the Night can be punishing if they hit you so make sure you avoid them whenever possible as you never know where the next health-restoring save point might be. The best strategy to defeat them without sustaining damage yourself, especially during boss fights since they are capable of dealing huge amounts of damage in a short period of time which even healing potions will not full replenish is to spend time studying their patterns to see if they have a weakness you can take advantage of.
Talk to NPCs
After major boss fights you will often be given helpful information by NPCs regarding how to reach the next area. Although they will not tell you exactly where to go they will give you clues such as items you might need, or obstacles you can now traverse. Two NPC's who are good sources of information are OD, the vampire who lives in the library, and Dominique, the Church agent in Arantville.
Try Different Weapons
There is a whole array of weapons that Miriam can use, these include swords, guns, battle-axes, knives, maces and whips. Each of these weapons has a different damage output, reach and speed. Make sure you try out as many different types of weapons as you can so you can find the ones that best suit your play style, whether it's keeping your distance with a gun or getting up close and personal with a dagger.
Boss Fights...