GS Companion
Swallowtail Sting

Swallowtail Sting

5★ Support Astral

Skill

40–46s CT - Increase all allies' Arts by 18–25.

Numbers in a range are rolled when the equip is crafted.

Crafting

Fusion Type
Astral: a Astral Glyph raises the chance
Extra effects
0–2 at random: ATK UP, HP Recovery UP, Skill CT Speed UP, Break Power UP, CRI rate UP, Accuracy UP, Arts UP, BE Output UP, PHY DMG UP, MAG DMG UP
Passive
3 of the same Crest Fragment can add that Crest's effect

Other 5★ Support Fusion Equips

Royal Navy
5★ Support Energy

40–46s CT - For 12s, increase all allies' Arts by 3/s.

Gemini Oracle
5★ Support Astral

40–46s CT - Increase ◯ Element allies' Arts by 21–30.

Twin Dawn Feather
5★ Support Energy

40–46s CT - For 12s, increase target's Arts by 7–9/s.

Quatro Flamme
5★ Support Energy

40–46s CT - For 12s, increase ◯ Element allies' Arts by 3–4/s.

Gear Stack
5★ Support Chronos

40–46s CT - For 12s, increase all allies' Skill CT Speed by 56–80%.

Bad Shuffle
5★ Support Chronos

40–46s CT - For 12s, increase all allies' Break Power by 49–70%.

Dark Scales
5★ Support Sense

40–46s CT - For 12s, increase all allies' Accuracy by 56–80%.

Tempter's Bangle
5★ Support Thanatos

40–46s CT - For 12s, increase all allies' CRI rate by 70–100%.

Tickling Muffler
5★ Support Buster

40–46s CT - For 12s, increase all allies' ◯ Element DMG by 56–80%.

Data from the Grand Crusade Guide by jeffers and .phex (Grand Summoners Official Discord).