One of the core mechanics of Cassette Beasts is fusion. They consist of the combination of monsters. Fusions are present as enemy encounters and can be created by the player as well.
Fusions gain the moves of both monsters they are derived from, have statistics based on the combined statistics of them, and gain 4 AP per turn. Therefore, they are immensely powerful. However, playing as one monster instead of two also means that only one move can be made per turn and they can be weighted down by debuffs.
When a fusion ends, either by willing unfuse or through fatal damage, all buffs and debuffs it had will be randomly distributed into its components, and will, in the case of Cassette Fusions, persist when transforming into other monsters. Note that buffs and debuffs present on the component monsters will not necessarily return to the original component, as they might be randomly given to the other one.
Both players and NPCs can fuse. When doing so, the resulting fusion will inherit all buffs and debuffs its components had. Identical buffs and debuffs that both components had will have their total duration added to one other, to a maximum of 16 turns.
Once the fusion takes fatal damage, it is dissolved and both of its components take fatal damage as well. Overspill damage can also harm and even knock out players.
The passive move, Cold Fusion will activate when a Cassette fusion is created.
- See also: Fusion Power
The game has a fusion meter which accrues power every time the player takes damage in a battle, and later upgrades bought from Ranger Wilma allow for other triggers to fill the fusion bar, such as winning a fight or landing a type advantaged attack. Once the bar is full, the player and their partner can fuse each of the monsters they play as into a combined form. The Pear Fussili consumable instantly fills the fusion bar, without spending a turn, which allows for an instant fusion on the spot.
Players can fuse once they reach relationship level 1 with a partner. Once the player reaches relationship level 2 with a partner, they can execute a special move called Fusion Power when you fuse with them. Fusion power demands the full AP bar to be used and are always incredibly powerful. Its exact nature (base damage, effects and if it hits a all enemies or a single target) depends on the components, coming in many varieties, such as Spike, Bomb, Sword, Axe, Wheel, Beam, Meteor, Wheel, and Smash.
The fusion must be performed during the turn of the main player, as it is not possible to select a move with the main player's monster and then fuse during the partner's turn. Fusions are temporally and battle only, and it is not possible to enter a battle fused (albeit one can fuse in the first turn). The act of fusing counts as an action, and debuffs such as Leech, Poison and Burn will proc. The fusion is able to immediately act, but this also counts as an additional action. As such, its important to mind certain debuffs, as they can activate twice in a row during the fusing turn; its even possible for a fusion to immediately suffer fatal damage the turn its formed if the components had damaging debuffs and were badly injured
The player is free to unfuse, safely breaking the fusion, on the second turn after originally forming it. It is not possible to unfuse immediately after initially fusing. Unfusing does not count as an action, and both components will be able to act in the same turn.
When unfusing, both monsters will have the same proportion of health as the fusion had left. This effectively means that their remaining health can change from what their original components had left, even if they received no damage while fused, as their HP pools will balance out.
It is not possible to record with a tape while in fused form, if the player wishes to record a monster, they must first unfuse.
Certain Cassette NPCs, notably Ranger Captains during their rematches, will also use fuse when down to their last 2 monsters. Other NPCs such as trainees and challengers posted in the Ranger Noticeboard in the postgame will usually fuse as well. NPC Fusions have access to Fusion Power, but they are not programed to unfuse, even when it is advantageous to do so. It's also possible to manipulate what the NPC fuses into as well as its timing, as it will always be when down to their 2 last. For example, the NPCs can be tricked into fusing when one of its components is under Gambit or Haunt (which some Captains utillize), which makes them knock themselves out, particularly as the fusing turn counts twice for their countdowns.
Fusions can also be encountered in the wild. They are found semi-randomly all over New Wirral, serving as minor boss encounters. When interacted with, the player will be prompted to fight them. Wild fusions cannot be recorded, but once the fusion's health is depleted it will split into its components, which may be recorded. All fusions have a dramatically increased chance of including bootlegs as one of their components.
Because Wild Fusions are encountered already fused, Cold Fusion will not activate when facing them, as the move demands a fusion to take place during battle to proc.
Unlike cassette-based fusions, wild fusions will dissolve after taking lethal damage, but their components will regain full HP. They gain Flinched for the next turn and inherit the buffs and debuffs the fusion had, spread randomly.
Wild fusions appear as a black, horned creature in the overworld, obscuring their real nature until engaged. Once the player obtains the Fusion Radar after becoming a Ranger and clearing the first task board, all fusions can be tracked. They are indicated by a black outline of a monster, and all look the same on the overworld regardless of the monsters fused. There are 4 different types of fusion encounters, which the Radar specifies:
Rogue Fusions are common boss encounters spread all over the map. The fusion will be typically made from monsters encountered in the area where it's found, though they have a 1% chance to instead be a species randomly chosen from the list of "Seen" species in the Bestiary. They also each have a 10% chance to be remastered if they can be remastered. The fusion might be accompanied by an additional monster, but this isn't always the case.
Rogue Fusions that spawn in certain locations can cause flooding in its vicinity. This flood can be lava, liquid poison, or water. The type of flood indicates that one of the monsters in the rogue Fusion is natively a Fire, Poison, or Water type respectively, randomly selected from a list of all monsters that are natively of that type.
Once defeated, Rogue Fusions will award the player with 1 Fused Material. Rogue Fusions have a 2% chance of including a bootleg monster as one of their components.
Fusion Swarms begin as sequential fight of 3 unfused monsters, which are then joined by 2 additional ones as they get knocked out (for a total of 5). Once at least 4 of them are defeated, the fusion will appear.
One part of this fusion will be one of the unfused monsters in the swarm (or a remaster of it), but the other part can be a different monster from the area. The fusion can also be made of the same monster twice.
Fusion Swarms appear from the beginning of the game, albeit they are less common than Rogue Fusions. It's not recommended to engage them too early, as the large number of monsters that must be fought in succession makes them a difficult fight before team hitting attacks and fusion are available to the player.
Once defeated, Fusion Swarms will award the player with 1 Fused Material. The fusion in these battles has 10% chance of containing a bootleg monster.
Unstable Fusions are fusions where one monster is Anathema, which appear after reaching level 3 in the Ranger Noticeboard. Defeating one is the first step of the Here Comes the Sun quest, after which they will naturally spawn over the map.
Unstable Fusions are drastically harder than regular Rogue Fusions, as Anathema is a naturally very powerful monster and it will always have Fission Power, which it will quickly attempt to use, doubling the already massive damage output of the fight. Additionally they always have a Random Starter, giving it an extra move instantly (which can include Fission Power). The Anathema component always has Self-Destruct as well, meaning that several explosions will take place over the fight, particularly if the split Anathema is also to use Fission Power. A copy created by Fission Power will not divide further, when its HP is depleted it will use Self-Destruction and die immediately.
The Anathemas fought as part of Unstable Fusions always have Self-Destruct, Random Starter, Fission Power, Pustule Bomb, Bite, Bloodlust and Desperation. All of these moves are inherited and available to the fusion.
Once defeated, Unstable Fusions will award the player with 1 Fused Material.
Orb Fusions are the most powerful form of fusions. They are unlocked after reaching level 6 in the Ranger Noticeboard and completing Here Comes the Sun. Orb Fusions are styled as proto-Archangels, and the fights with them include the Archangel musical theme and glitch effects.
When engaged, the fusion is protected by an Orb, which obscures the monster (albeit its components can be deduced based on its name and types). The player must first break the Orb, serving as an entire additional health bar. Whilst enveloped in the Orb, the fusion will use Archangel mechanics: its AP won't be consumed by moves, and once it hits a full bar it will attempt to use Fusion Power. The Orb also provides Archangel immunity to to certain debuffs such as Petrified and Sleep. Once the orb breaks, the Fusion will be exposed and it will start to consume AP normally and lose archangel immunity, but it will be unharmed and able to fight immediately.
Orb Fusion fights are by far the most difficult as the first stage has a massive damage output and the threat of Fusion Power quickly ramps up, on top of being a debilitating attrition fight as the player has to fight through 4 health bars to win (Orb, Rogue Fusion and each of the components), but they award 5 times more Fused Material.
Once defeated, Orb Fusions will award the player with 5 Fused Material. Orb Fusions have the highest odds of containing a bootleg monster, at 20%.
Fusion is a mysterious phenomenon unique to New Wirral. It is hard to do, and even the Ranger Captains are impressed by the player's mastery of it. Post-game, the player discovers more about the origins of fusion when undertaking Helia's quest Here Comes The Sun.