Greedy, treacherous sellswords of the lower planes who fight for demons and devils alike, and switch sides the moment someone offers a better price.
In the great planar city, ambition is admired and a little backstabbing on the road to riches is forgiven, even praised as hard-won wisdom. Yet one insult still makes the most cheerful rogue bristle: being called 'not worth a mercenary fiend.'
These fiends live on the lower planes: a plane of endless war, a volcanic lower plane, the gray wasteland of despair, and the prison plane. They hire out to both sides in the endless war between demons and devils with no loyalty whatever, readily turning on an employer who is outbid. Anyone using them in battle had better hold real power over them first.
Greater mercenary fiends are officers who rule by raw strength. Lesser ones form the rank and file and work hard for promises of wealth and power. Various guardian types also exist. They squabble constantly, and though each is a savage fighter alone, they make poor soldiers in formation. Baatezu and tanar'ri hire them chiefly because each side fears what the other could do with them. Word of their betrayals seldom reaches the hells or the Abyss, but when it does, the turncoats are tracked down and tortured horribly, which does nothing to curb their avarice.
Lost among the sulfur barrens of the volcanic lower plane roams a mastermind fiend so mighty that nothing there dares oppose it: the Warlord of the Smoking Wastes, master of that entire realm. Many mastermind fiends seek it, believing service at its side brings status among the fiends. No one finds it unless it wishes, and its true name appears nowhere, not even in the oldest tome of binding.
Weapons and other attack forms affect these fiends as listed on their table; ordinary weapons deal full damage. At will, every one of them can use produce flame, charm person, teleport without error, animate dead, improved phantasmal force, alter self, and cause disease (the reverse of cure disease). They may also gate in others of their kind, but this cuts both ways: each one called has a 25% chance to betray its summoner and side with the enemy, then beg a reward if that enemy triumphs.
As natural servants they are frequent targets of conjuration. A mage summoning a lower-planar being has a 40% chance of getting a mercenary fiend; otherwise a fiend of the prison plane answers. An ancient work of unknown authorship, the Ledger of Binding, details how to call and control both greater and lesser kinds and even records true names of some greater ones. Speaking such a name without strong protection invites the named fiend to strike the caller down and consume his life force. Four or more copies survive, whereabouts unknown, and only a conjurer specialist can use one. Even skilled conjurers struggle to bind the greater fiends, which never forget a slight.
More: Monsters starting with M · Planescape monsters · All monsters A-Z
Related: Clatter Fiend [Lesser Mercenary] · Elder Fiend [Greater Mercenary] · Ferryman Fiend [Lesser Mercenary] · Guardian Fiend · Hound Fiend [Lesser Mercenary] · Mastermind Fiend [Greater Mercenary] · Oathkeeper Fiend [Lesser Mercenary] · Overseer Fiend [Lesser Mercenary] · Ravager Fiend [Lesser Mercenary] · Scholar Fiend [Greater Mercenary] · Soldier Fiend [Lesser Mercenary] · Water Fiend [Lesser Mercenary]