While combining two or more atma with the same element doesn't directly provide bonus attributes, it is worth mentioning that atma from the same element share similarities and synergize with each other. Here is a list of some that I have observed:

Fire

• Generally high DPS, such as Rama, Lohita, and Srikandi, with relatively low HP

• Benefits from CRIT and CRD, especially Srikandi and Agni's anti-cleave passives

• Agni's [FIRE BLESSING] not only provides a vital CRIT buff, but also procs Rama's [VIGOROUS TECHNIQUE]

• Srikandi and Wisanggeni's BURN debuff may further proc ATK DOWN and VENOM from the latter

Water

• Somewhat tanky units, with medium to high base HP and/or anti-cleave DEF UP buffs as well as BLOCK UP

• Anggatri's and Sura's FREEZE can proc: Kandita's [CRYOSPHERE], extra damage and SPEED DOWN debuff from Kandita's [HIMA SAMUDRA], and amplify Kresna's BLEED

• ATK UP buff from Anggatri's [MYSTIC SERPENT] can proc Kandita's [ROYAL DECREE]

• Anti-BURN (Anggatri and Kresna)

Wind

• Relatively squishy, with low base HP and/or taunt skills

• Garuda's passive SPEED UP can be distributed to the backline thanks to Drona's [SWIFT DRAFT]. SPEED UP procs Hanuman's [SWIFT CRIT] as well as Amritha's [SWIFT SWIPE]. Devastating to the enemy backline.

• Anti-PETRIFY (Shinta, Amritha, Hanuman)

Earth

• Medium to low base HP

• Inflicts hefty DEF DOWN (Rahwana's [KING OF THE THREE WORLDS], Sweta's [DOLL-EYED], Timun Mas' [NEEDLE BAG])

• ATK up benefits Rahwana's AOE [BRAVE CLEANSING] and Lampir's [LAVA'S EDGE]

• Anti-FREEZE (Lampir, Rahwana)

• Jack-of-All-Trades; Earth element atma don't really synergize with each other, but can generally fit in formations with/vs other atma and elements

Sun

• SPEED UP from Cindaku's [FOREST'S WRATH], or from Sembrani's [QUICK WINGS], can proc: Barong's [SWIFT AEGIS], Gatotkaca's [SWIFT DRAFT], Sembrani's [SWIFT VIGOUR], as well as Cindaku's own passive [SWIFT DISPEL] and [CRIPPLING DART].

• DEF UP from Barong's [SWIFT AEGIS] can proc: STUN debuff if Barong takes damage, or Gatotkaca's [REINFORCED TAUNT], or Vrahatnala's [REINFORCED CORROSIVES].

• Debuffs from Cindaku's [CRIPPLING DART], Barong's [ATMA PALAKA] and [COVER STRIKE], as well as Vrahatnala's own passives, prepare the perfect target for Vrahatnala's [ASTRA DHAVITRA]

Moon

• Somawari plays a vital support role in the formation. He can inflict SPEED DOWN, and provides CRIT and CRD buffs to his team, laying out the path for the main DPS units.

• Sandekala's passive [TIME IS OVER] deals extra damage to enemies with SPEED DOWN.

• CRIT buffs from Somawari can enable Sandekala to inflict BLEED on a target. Targets inflicted with BLEED receive extra damage from Noni's [ASTRAL NEGATION].

• CRIT buffs from Somawari also increase Noni's chances to stack up CRD buffs, often able to reach lethal heights.

• Moon atma are able to strike multiple times thanks to EXTRA TURNs. If Sandekala eliminates an enemy with [SPIRITED AWAY], they gain an extra turn with fully recharged energy. Noni's [MIRAGE RIPPLE] provides an extra turn to her and at least 1 ally if she lands a CRIT hit. Antasena's anti-cleave [WARRIOR'S BOND] provides all allies in one row an extra turn.

• Anti-STUN (Noni, and Antasena from a certain point of view)

Please note that some atma may not fit very well in their own elemental formations, such as Surti or the Earth atma. If you have any suggestions or criticism, please let me know in the comments!