Mercs are allies (can be Linked)
Mercs are NOT party members
Mercs are NOT minions
Keystones and Notables from gear do work with mercs
Triggers don't work with socketed skills due to merc skill system
Curse limit is per enemy, so you or merc need +1 limit to have 2+ combined curses
General ideas:
Curse on hit (Curse on hit rings, gloves; Anathema curse limit)
Charge generation (Conduit doesn't work)
"Nearby" effects
MF + Gravebind
Rings
Doedre's damning (Additional curse)
Grattus signet (Attacks unnerve, spells intimidate)
Call of the Void (Enemies chilled by your hits lesson damage by half chill effect)
Blackflame (Wither does not expire on enemies ignited by you)
Icefang Orbit (Non-chilled enemies you poison are chilled)
Venopuncture (Non-chilled enemies you bleed are chilled)
Polaric Devastation (Left, cover enemies in Ash when you ignite them; right, cover enemies in Frost when you freeze them)
Amulet
Perquil's Toe (nearby allies damage is lucky; 5M)
Yoke of Suffering (Enemies take (5-10)% increased Damage for each type of Ailment you have inflicted on them)
Aul's Uprising (Hits against Nearby enemies have 50% inc crit chance; 6M)
Shaper's Seed (Nearby allies inc 80% mana regen, regen 4% life per sec; 4.6M)
Eternal Struggle (15% cull w/ exarch)
Pandemonius (Blind chilled enemies on hit)
Xoph's Blood (Cover enemies in Ash when they hit you)
Xoph's Heart (Nearby enemies are covered in ash)
Ignomon (Nearby enemies are blinded; ??M)
Corruption implicit (Additional curse)
Belt
Kaom's Binding (Nearby enemies convert 25% phys to fire; 6M)
Belt of the Deceiver (Nearby enemies intimidated; 2.5M)
Gluttony (Cull vs cursed enemies)
Gloves
Ceaseless Feast (corrosion -armor debuff, endurance/frenzy charges)
Lochtonial Caress (Conduit)
Asenath's Gentle Touch (Curse w/ temp chains on hit, explosion)
Gravebind (Nearby enemies killed by anyone count as killed by you instead; 4M)
Vixen's Entrapment (Additional curse)
Weapon
Oro's Sacrifice (Frenzy on igniting an enemy)
The Red Trail (Frenzy)
Replica Tulfall (Frenzy/power w/ freeze)
Terminus Est (Frenzy on crit)
Kingmaker (Nearby 10 fort, cull; 3M)
Singularity (100% increased Damage against Hindered Enemies; 3.5M hinder)
Dying Breath (Nearby enemies 18% inc curse effect on them, allies 18% inc non-curse aura effect; 7.5M)
Sign of the Sin Eater (Enemies inflict ele ailments on you instead of nearby allies; 6M)
Shield
Redblade Banner + Enduring Cry
Victario's Charity (10% grant power charge to ally on kill, 5% grant frenzy on hit; 4M)
Replica Victario's Charity (10% Frenzy charge to ally on kill, 5% endurance on hit; 4M)
Brinerot Flag (Warcries grant Arcane Surge to you and allies, 10% inc effect per 5 power max 50%)
Anticipation (Permanently intimidate enemies on block)
Dawnbreaker (Scorch enemies in close range on block)
Sentari's Answer (Curse w/ punishment/temp chains/ele weak upon blocking melee/proj attack/spells, respectively; ignores curse limit)
Deep One's Hide (Curse w/ vuln on block)
Body
Doppelgänger Guise (10% regen when hit, 30-40% less phys/chaos taken)
Doryani's Institute (Nearby negative lightning res; 6M)
Cospri's Will (Additional curse)
Expediton's End (Nearby enemies chilled; 3M)
Belly of the Beast (40% max life and 15% ele res for merc)
Garb of the Ephemeral (Nearby enemies can't crit; 6M) & (Nearby allies min 100% action speed; 5M)
Hunter prefix (Additional curse)
Helmet
Blood Price (Reserve 8% nearby enemy life; 3M)
Thundersight (Sap enemies)
Flamesight (Scorch enemies)
Galesight (Brittle enemies)
Crown of the Tyrant (Nearby -10 ele res, nearby allies +flat dmg; 6M)
Leer Cast (Nearby 50% increased damage; 7.5M)
Eye of Malice (Cold/Fire exposure, nearby 1.5x cold/fire res (can scale negative); 2.9M)
Boots
Windscream (Additional curse)
Legacy of Fury (Nearby enemies scorched; 3M)
Aura Range
Dying Breath
Victario's Charity
Victario's Influence
Approx distance to side of monitor on 16 : 9 - 8.5M
So top/bottom would be right around 5M
Conduit sharing range - 12M
Most auras - 5.5M
Soul Eater - 5M
https://www.poewiki.net/wiki/Distance#NearbyEldritch implicits - exposure, unnerve, intimidate on hit