Serif

Strategy
(Note that her HP and Defense increase to 10400 and 8 respectively if you're playing as the Shopkeeper)

Patterns

 * Starts the fight by removing the usual grid restriction that prevents the player from moving to the enemy's side of the grid and vice versa, instead turning the entire grid a gray color and allowing the player character to move anywhere on the grid: Should they advance to the right side of the grid, they (as well as their spells) will begin facing left.
 * Occasionally precedes an attack by spawning a few Light Bombs on the grid: These are structures which have 40 HP and fire a bullet in the four cardinal directions when destroyed. Note that they can be damaged and destroyed by Serif's attacks, requiring the player to dodge the bullets as well as her regular attack.
 * Swords made of light appear at her sides, turning the entire column she's in into a damaging hitbox, then charges toward the side of the grid the player character's in, stopping one column before the edge of said side of the grid.
 * Rains down 3 shots on the grid that split twice, hitting the 4 tiles around them in the cardinal directions each time, similarly to . At low HP, this attack may be repeated a few times.
 * Swords made of light appear at her sides, turning the entire column she's in into a damaging hitbox, then charges toward the side of the grid the player character's in, stopping one column before the edge of said side of the grid.
 * Rains down 3 shots on the grid that split twice, hitting the 4 tiles around them in the cardinal directions each time, similarly to . At low HP, this attack may be repeated a few times.
 * Rains down 3 shots on the grid that split twice, hitting the 4 tiles around them in the cardinal directions each time, similarly to . At low HP, this attack may be repeated a few times.
 * Rains down 3 shots on the grid that split twice, hitting the 4 tiles around them in the cardinal directions each time, similarly to . At low HP, this attack may be repeated a few times.






 * Pushes the player character towards one side of the grid, then launches several 2-tile high waves of light towards the player, traveling at high speed.
 * Pushes the player character towards one side of the grid, then summons a Light Bomb before launching a wave of 4 light swords (one for each row) towards the player character. This is followed by more waves of 3/2/1 light swords.
 * Pushes the player character towards one side of the grid, then summons a Light Bomb before launching a wave of 4 light swords (one for each row) towards the player character. This is followed by more waves of 3/2/1 light swords.
 * Pushes the player character towards one side of the grid, then summons a Light Bomb before launching a wave of 4 light swords (one for each row) towards the player character. This is followed by more waves of 3/2/1 light swords.


 * Spawns a light sword in a tile close to the player, then flies to it, swinging it in a 5x5 area after reaching it, similarly to how behaves.
 * Launches light swords from the top and bottom side of the screen.
 * Launches a very large number of light swords in a sweeping maneuver from both sides, two sweeps start from each side. The column furthest away from her is generally safe.
 * Pushes the player character towards one side of the grid, then launches light swords towards them in quick succession. At low HP, light swords are also launched from above the grid.
 * Launches light swords from the top and bottom side of the screen.
 * Launches a very large number of light swords in a sweeping maneuver from both sides, two sweeps start from each side. The column furthest away from her is generally safe.
 * Pushes the player character towards one side of the grid, then launches light swords towards them in quick succession. At low HP, light swords are also launched from above the grid.
 * Launches a very large number of light swords in a sweeping maneuver from both sides, two sweeps start from each side. The column furthest away from her is generally safe.
 * Pushes the player character towards one side of the grid, then launches light swords towards them in quick succession. At low HP, light swords are also launched from above the grid.
 * Pushes the player character towards one side of the grid, then launches light swords towards them in quick succession. At low HP, light swords are also launched from above the grid.
 * Pushes the player character towards one side of the grid, then launches light swords towards them in quick succession. At low HP, light swords are also launched from above the grid.








 * Summons Light Bombs covering the top and bottom row of the grid, then hits one of them, causing a chain reaction of bullets.










 * Fires a shot directly at the player's spell slots, the spell it hits. Shuffling or otherwise having no spell in the slot when the shot hits avoids this.

Beating Serif will cause her to recover 3000 HP, then send the player back in time to the first world, looping the game. If the player has killed the Shopkeeper or is playing as her, their spells are replaced by several "Yami" spells, which deal large amounts of damage to Serif in this state and can kill her, completing the Genocide route and unlocking Saffron's "Solo" loadout, if playing as her and if not already unlocked.

Trivia

 * Her name sounds like "Seraph", a multi-winged angel.
 * Her name is also likely based on "serifs", which are projections sticking off of strokes in many typefaces.
 * By removing the grid restriction and allowing the player to turn around, Serif frequently places the player character on the right side of the grid, normally reserved for the enemy. This alludes to the player's villainous role in the Genocide route.
 * Appropriately, this doesn't happen during the Serif encounter in the Neutral route - though Serif still fights them, the player character has spared at least one person, and is therefore not placed in the role of the "villain."
 * By removing the grid restriction and allowing the player to turn around, Serif frequently places the player character on the right side of the grid, normally reserved for the enemy. This alludes to the player's villainous role in the Genocide route.
 * Appropriately, this doesn't happen during the Serif encounter in the Neutral route - though Serif still fights them, the player character has spared at least one person, and is therefore not placed in the role of the "villain."