Sandalphon/Strategy

Strengths

• Superior offensive and defensive capability from  This is What I Live ForCan't restore HP.
  Takes 10% max HP damage every turn (Damage cap: 1000).
  100% / 30% boost to critical hit rate100% chance of dealing 30% more damage. and 20% boost to damage cap.
  250% boost to DEF.
  Guaranteed double attacks.
  Converts some types of turn-based damage to HP recovery.:
  • High damage cap, guaranteed critical hit against Water and non-elemental foes, and guaranteed double attacks.
  • High innate defense.
  • Heal up to 1000 HP per turn.
  • Resilient against most turn-based damage and convert it to healing instead (e.g PoisonedHP is lowered on every turn
    , BurnedHP is lowered on every turn
    ).
• Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
  Local status effect has unique capability to transform foe's element into Water, allowing
  
  Earth Seraphic Weapon
  • Gauntlet of Uriel (SR)
  • Gauntlet of Uriel (SSR)
  • Gauntlet of Proudearth
  to work against non-Water foes.
  • In conjunction of that debuff, he also inflicts Prison of WarCharge diamonds don't fill up / Can't use special attacks
    Local status effect, stopping most foe's special attacks for two whole turns.
• Ability to grant himself unremovable Elemental ATK UpFire ATK UpFire ATK is boosted (Can't be removed)
  
  Water ATK UpWater ATK is boosted (Can't be removed)
  
  Earth ATK UpEarth ATK is boosted (Can't be removed)
  
  Wind ATK UpWind ATK is boosted (Can't be removed)
  with  Ecliptica600% Earth damage to a foe (Damage cap: ~630,000).
  Steal one of the tetra-elements.
  (Inflict 30% Fire ATK DownFire ATK is lowered
  Strength: 30%Base Accuracy: 100%Duration: 180 seconds, 30% Water ATK DownWater ATK is lowered
  Strength: 30%Base Accuracy: 100%Duration: 180 seconds, 30% Earth ATK DownEarth ATK is lowered
  Strength: 30%Base Accuracy: 100%Duration: 180 seconds, or 30% Wind ATK DownWind ATK is lowered
  Strength: 30%Base Accuracy: 100%Duration: 180 seconds on a foe.
  Gain 30% Fire ATK UpFire ATK is boosted (Can't be removed)
  Strength: 30%Duration: Indefinite, 30% Water ATK UpWater ATK is boosted (Can't be removed)
  Strength: 30%Duration: Indefinite, 30% Earth ATK UpEarth ATK is boosted (Can't be removed)
  Strength: 30%Duration: Indefinite, or 30% Wind ATK UpWind ATK is boosted (Can't be removed)
  Strength: 30%Duration: Indefinite based on the stolen element.) and instantly benefits from it with bonus damage from his  Four Primarchs' Wings30% Bonus DMG effect of each stolen element.
  Buffs can't be removed once Sandalphon has all the tetra-elements., although gained buff is random and can be regained.
  • Once he gains all of the possible buffs, other buffs granted to him cannot be removed.
• By sacrificing allies' buffs, he can remove buffs from all foes with  The ViceRemove all buffs from all other allies and foes.
  Gain Instant ChargeInstantly sets Charge Bar to 100%
  Unaffected by Charge Bar Gain status effects.
  No effect when afflicted by Shorted debuffs or when Charge Bar is above 100%., 150% C.A. DMG UpCharge attack DMG is boosted (Can't be removed)
  Strength: 150%Duration: 1 turn , and 90% C.A. DMG Cap UpCharge attack DMG cap is boosted (Can't be removed)
  Strength: 90%Duration: 1 turn ., giving him instant charge attack with high magnitude.

Weaknesses

• The downtime of Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
  Local status effect is fairly high, making him unsuitable for longer off-element battles.
• While Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
  Local status effect transform foe's element for remainder buff duration, it does not remove elemental resistances.
• Both Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
  Local status effect and Prison of WarCharge diamonds don't fill up / Can't use special attacks
  Local status effect are local status effects. They only benefits the caster's party.
•  This is What I Live ForCan't restore HP.
  Takes 10% max HP damage every turn (Damage cap: 1000).
  100% / 30% boost to critical hit rate100% chance of dealing 30% more damage. and 20% boost to damage cap.
  250% boost to DEF.
  Guaranteed double attacks.
  Converts some types of turn-based damage to HP recovery. prevents him to receive healing normally; he only heals from turn-based damage.
• Requires micromanagement on determining time to cast  The ViceRemove all buffs from all other allies and foes.
  Gain Instant ChargeInstantly sets Charge Bar to 100%
  Unaffected by Charge Bar Gain status effects.
  No effect when afflicted by Shorted debuffs or when Charge Bar is above 100%., 150% C.A. DMG UpCharge attack DMG is boosted (Can't be removed)
  Strength: 150%Duration: 1 turn , and 90% C.A. DMG Cap UpCharge attack DMG cap is boosted (Can't be removed)
  Strength: 90%Duration: 1 turn . due to very scarce source of unremovable party-wide buffs on Earth.

Unremovable Buffs

Having allies which grants allies unremovable buffs or ability to retain their buffs allows him to cast  The ViceRemove all buffs from all other allies and foes.
Gain Instant ChargeInstantly sets Charge Bar to 100%
Unaffected by Charge Bar Gain status effects.
No effect when afflicted by Shorted debuffs or when Charge Bar is above 100%., 150% C.A. DMG UpCharge attack DMG is boosted (Can't be removed)
Strength: 150%Duration: 1 turn , and 90% C.A. DMG Cap UpCharge attack DMG cap is boosted (Can't be removed)
Strength: 90%Duration: 1 turn . more frequently without worrying too much with his buff-removing capability against his own allies. Few sources of it are:

• Cain (Grand):  Soldier's SwiftnessAll allies gain InstantaneityATK is boosted /
  Double attack rate is boosted /
  Triple attack rate is boosted
  (Can't be removed)
  Strength: 30% ATK Up / 20% DA Up / 10% TA UpMultiplier: NormalDuration: 6 turnsSpecial buff.
• Golden Knight:  Golden ArmorRecover 5% of max HP each turn (Healing cap: 500). Gain 10% Charge BoostInstantly boosts Charge Bar by 10%
  Strength: 10% if HP is full.
  Buffs can't be removed.
• Jessica (Yukata):  FeuerwerkAll allies gain FeuerwerkATK is boosted /
  DEF is boosted /
  Double attack rate is boosted /
  Triple attack rate is boosted
  (Can't be removed)
  Multiplier: NormalDuration: 3 turnsSpecial buff and 10% Debuff Success BoostedDebuff success rate is boosted
  Strength: 10%Duration: 3 turns.
  When Fire SupportPflegeschuss and Godsend Trigger's DMG and DMG caps are boosted (Max: 2 times / Can't be removed)
  lvl is 1 or higher: All allies also gain Supplemental DMGDMG dealt is supplemented
  Strength: 1% of foe's max HP (Damage cap: 30,000)Duration: 3 turns.
• Mahira:  Spirit DrumsAll allies gain Zeal of the FeatherATK is boosted / DEF is boosted /
  Triple attack rate is boosted / Double attack rate is boosted /
  C.A. DMG Cap Boosted (Can't be removed)
  Multiplier: NormalDuration: 5 turns.
  (Consumes all Drum BeatGain stars by attacking foes
  (Boost to Spirit Drums based on the number of stars)
  . Effect varies based on number of Drum Beat consumed.)
  At level 95:
  Zeal of the FeatherATK is boosted / DEF is boosted /
  Triple attack rate is boosted / Double attack rate is boosted /
  C.A. DMG Cap Boosted (Can't be removed)
  Duration: 5 turns now always has maximum effectiveness.
  Drum BeatGain stars by attacking foes
  (Boost to Spirit Drums based on the number of stars)
  is no longer consumed upon cast.
• Melleau:  Me and My PartnerRaise Warrior's WrathDEF is boosted (Can't be removed)
  Duration: Indefinite lvl upon triple attacks.
  (Gain in order based on lvl: 100% boost to DEF, 20% reduced damage taken, +20 boost to hostility, charge bar fills up 100% faster from damage taken, buffs can't be removed.)
• World Ender (4★/Main):  VernusMassive Earth damage to a foe.
  All Earth allies gain Counters on DMG (3 times)Counters upon taking DMG
  Strength: 200%Counter attacks grant 5% charge bar per hit..
  After 4★:
  All Earth allies also gain Dispel CancelEffects that remove buffs will be nullified (1 time)
  .
• Zeta and Vaseraga (Halloween):  Festive ContractorsGuaranteed double attacks.
  Zeta and Vaseraga's buffs can't be removed.
• Monika (Valentine):  Lovely DressingAll allies gain RefreshHP is restored on every turn
  Strength: 1000Duration: 3 turns and VeilDebuffs will be nullified (1 time)
  Duration: Indefinite"Veil" is an unofficial name used by the wiki for this status effect. Its actual in-game name is "Immune.".
  (When Monika has 12 or more buffs:
  All allies also gain Dispel CancelEffects that remove buffs will be nullified (1 time)
  Duration: Indefinite.)

Elemental Boost

With Sandalphon's Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
Local status effect, weapons and summons which only benefits against Water foes can be safely used which in turn increase the party's firepower for the remainder of turns. Notable examples are:

• Gauntlet of Proudearth
• The Hanged Man (SSR) (Sub)

Other

• Lobelia:  Warbringer900% Earth damage to all foes (Damage cap: ~1,120,000).
  3-turn cut to Earth allies' skill cooldown.
  (Consumes 5 Magic CrestMagic is amplified (Can't be removed)
  .)
  At level 75:
  Damage increased to 1000% can potentially make Elemental FrictionOriginal element has been lost and water element has been gained instead / Deals water DMG (Excludes plain DMG / Can't be removed)
  Local status effect have permanent uptime.
• Golden Knight: can also make use of  The ViceRemove all buffs from all other allies and foes.
  Gain Instant ChargeInstantly sets Charge Bar to 100%
  Unaffected by Charge Bar Gain status effects.
  No effect when afflicted by Shorted debuffs or when Charge Bar is above 100%., 150% C.A. DMG UpCharge attack DMG is boosted (Can't be removed)
  Strength: 150%Duration: 1 turn , and 90% C.A. DMG Cap UpCharge attack DMG cap is boosted (Can't be removed)
  Strength: 90%Duration: 1 turn . via their skill,  Sword in FluxReplicate caster's or an ally's skill.
  (Gains a buff based on the type of skill replicated.)
• Monika (Valentine): her  Wind of Love's SparkAll allies gain Charge Bar +30%Instantly boosts Charge Bar by 30%
  Strength: 30% and 20% Charge Bar Gain UpCharge bar gain is boosted
  Strength: 20%Duration: 3 turns.
  (When Monika has 12 or more buffs:
  All allies also gain 80% C.A. DMG Up (1 time)Charge attack DMG is boosted (1 time)
  Strength: 80%Duration: Indefinite and 20% C.A. DMG Cap Up (1 time)Charge attack DMG cap is boosted (1 time)
  Strength: 20%Duration: Indefinite.) can allow Sandalphon to use  Ain Soph Aur450%Massive Earth damage to a foe.
  Gain BlessedNext Ecliptica activates twice (Can't be removed)
  Duration: Indefinite. (Next Ecliptica activates twice.) more often.