Cat

Cat (also known as Byakko or Bai Hu) is a summoning magic spell ability used as a sub-weapon by Maria in Castlevania: Rondo of Blood and Portrait of Ruin, and by Soma in Aria or Sorrow and Dawn of Sorrow with a Student Witch soul. The ability summons a cat that runs along the floor damaging any enemy that gets in its way, until it hits a wall or exits the screen. This cat is a miniature version of Byakko, a white tiger from Japanese Mythology with black stripes. The item crash for the cat unleashes the great Byakko himself, which has different incarnations depending on the game. Byakko was originally a Chinese constellation known as Bái Hǔ the White Tiger. It was one of the "Four Symbols" and represented the West and the Autumn season.

Castlevania: Rondo of Blood
A white black striped cat leaps from Maria's arms and runs along the ground charging at any enemies in its path. If it strikes an enemy, it is stunned for a second, then leaps a little and continues moving forward. After a while it disappears. If it runs into a ledge, it will be stunned and then try to jump over it if it is small enough. It is found at the same locations where Richter would find an Axe.

Its item crash involves Maria riding Byakko, the giant white tiger. The tiger starts on the ground level, then turns around at the end of the screen and races mid-screen, then reaches the end again, turns around, and races at the top of the screen.

Castlevania: Symphony of the Night (Saturn)
The cat in the Sega Saturn version of Symphony of the Night is not a sub-weapon and does not resemble the cat found in Rondo of Blood. Instead, it is a spell that Maria can use at any time. Maria calls upon the spirit of the Byakko, the white tiger, which allows her to cast a great spell of flames that come out of her hand. Maria is invulnerable while the spell is being cast.

Castlevania: Aria of Sorrow
Student witches can toss purple cats at you. When taking their souls, Soma can duplicate this ability which is similar to Maria's cat sub-weapon. However, it is blue (to match Soma's color), unlike Maria's white tiger-striped cat.

It has 1/8 chance to throw a kitten instead of an adult cat. This is merely an aesthetic change, however, as it doesn't change its attack power.

Castlevania: Dawn of Sorrow
As in the previous game, Soma can steal a Student Witch's soul to give him the ability to release a charging black cat.

Castlevania: Portrait of Ruin
Maria's black and white cat is released and charges at enemies. In this game, it keeps on running through enemies instead of bouncing off of them. It also deals electric damage, causing massive damage to armor type enemies which are vulnerable to its ground based attack. The cat stops moving once it hits a wall and then disappears. It also disappears once its time has run out.

Castlevania: The Dracula X Chronicles
In this game, Maria's cat behaves more like it did in the original Rondo of Blood and it's 3-D remake. It tries to jump over ledges and attacks enemies multiple times if they get in its way. For its item crash, a giant symbol for Byakko, the white tiger, appears and then the tiger appears behind Maria. For a time, whenever she attacks using her owls, tiger's claw swipe marks appear at various distances in front of her.

Castlevania: Harmony of Despair
Maria's cat appears as it does in Portrait of Ruin and deals out lightning damage.