When using a Unite Move, shield yourself and your nearby ally with the lowest HP.
In-game description: When the Pokémon uses its Unite Move, that Pokémon and the nearby ally Pokémon with the lowest HP are each granted a shield equal to 20% of their max HP.
20 -> 400 (lvl 20)
Maximum Health Points. [Estimated max value]
Shield (Upon Unite)
20% -> 40% (lvl 20)
Upon using a Unite Move, the attacker and its lowest-HP ally gain a shield of a percentage of their respective maximum HPs.