Cheer is a Bard ability in the NES version, which increases the damage done by the party's physical attacks.
Guardian Forces' attacks are enhanced by Boost via timed button presses. The GFs Diablos, Carbuncle, Cerberus, and Cactuar do not have Boost, since their effects either do not deal damage, or do a set amount of damage. A character's compatibility with a GF determines how much they can boost it before the animation ends. Removing Boost with Amnesia Greens is not recommended, as there is no way to regain the Boost ability.
During the summon animation, the player can hold down the button and tap the button to boost the GF to increase damage; the drawback is that if the player fails to boost the GF, it may end up dealing less damage than it would have when not boosted at all. The damage varies between 75% and 250% of the normal damage. The percentage rises when the player taps the button correctly, but drops to 75% if the player presses the button during a time a red cross appears over the cursor. GFs with longer summon animations, such as Eden, are the easiest to boost.
Boost is a support ability that enhances Garnet's and Eiko's summons, showing the full summon animation each time an eidolon is summoned. Garnet can learn it for 190 AP, while Eiko can learn it for 150 AP, both from the Pumice Piece. It takes 12 Magic Stones to equip.
Boost is a special ability that comes in three levels of power. During Battle Music Sequences if the player is successful in calling a summon, Boost powers up their attacks up, higher levels of Boost granting a larger benefit. Boost is learned by Cid, Rydia, Yuna and Cosmos at all levels of power.
Boost (Lv1) is a reactive ability that costs 8 CP to equip. It is activated in Battle Music Sequence (BMS) with a successful summon to increase the summon's attack power and has low strength. It is learned by Rydia (level 5), Terra (level 25), Aerith (level 15), Garnet (level 15), Yuna (initially), Aphmau (level 10), Cosmos (level 15), and Ace (level 5).
Boost (Lv2) is a reactive ability that costs 14 CP to equip. It is activated in BMS with a successful summon to increase the summon's attack power and has medium strength. It is learned by Rydia (level 30), Terra (level 60), Aerith (level 45), Garnet (level 65), Eiko (level 50), Yuna (level 35), Aphmau (level 45), Hope (level 75), Cosmos (level 50), and Ace (level 50).
Boost (Lv3) is a reactive ability that costs 20 CP to equip. It is activated in BMS with a successful summon to increase the summon's attack power and has full strength. It is learned by Rydia (level 60), Eiko (level 90), Yuna (level 75), and Aphmau (level 90).
Boost ATK for all allies.
Appearing alongside Cheer and Focus, Boost is an special ability that allows the caster to increase, for three turns, the whole party's ATK by 40%. Gilbert is the only unit that can learn Boost; he obtains the skill at Level 57 (5★).