zenith raptor
Based off of the name for joint-magic attacks in Fairy Tail, Unison Raids are powerful combo attacks that require two or more units to use! This would add even more synergy between units, namely units from the same series.
Unison raid will appear to the right of compatible units’ abilities. Both units participating in a unison raid have this button appear. (You will select unison raid then the compatible unit you wish to perform it with). The range of the unison raid is based on the unit you hit the unison raid button from. (Similar to fusing in that game).
Unlike passive synergies like SJW + Igris, whose passives benefits can be kept up permanently or indefinitely, Unison Raids are specifically attacks that require both those units to use. These attacks (naturally) are stronger than any of these units individual attacks, and could even carry secondary effects! These unison raids also have the potential to use BOTH of the units elements when considering interaction with an enemy, or a different element entirely!
Unison Raids would require some form of requirement to meet before use, I.E. using an ability X amount of times, reaching a certain number of takedowns, being stunned, and effectively anything that can happen in a stage. Even out of stage requirements like a quest or achievement to unlock the ability to use unison raid for specific units, like reviving x amount of enemies with arise, or killing enemies during the duration of unlimited void. Once a unison raid is used, its requirements must be met again to use.
This mechanic helps add tons of personality to unit interactions and build variety for team comps, and is naturally balanced around more powerful unison raids potentially needing more than two units to use, meaning the comp effectively is built around the units needed, that itself adding a new way to play the game.
Unison raids do not have to be 100% canonical to their origin series, allowing a more unique take on synergy than other td’s.
Here are some examples of potential Unison Raids!
SJW + Igris: A combo attack that instantly turns killed enemies into shadow knights, these specific shadow knights have improved hp compared to their arise counterparts.)
(Requirement: Igris kill’s enemies when buffed by shadow knights being in his radius)
Naruto + Sasuke: A combo attack that is considered blast element, repulses enemies back, after the repulse finished, enemies are stunned for 1.5s. Enemies that are stunned spread the effect to nearby enemies, up to two times.
(Requirement: enemies are killed while stunned/frozen)
Ram/Rem + Emilia: a combo attack that freezes enemies in a half radius, then an attack that has 100% crit chance, crit damage is increased by 35% for 20s after this ability.
(Requirement: Land Critical Hits on frozen enemies)
high spire
wanton parrot
coral pulsar
and i made this type of attack / ability in my suggestion