Suikoden is a multimedia franchise created by Konami. Not really at all based on the novel Water Margin, Suikoden is the story of several civil wars across multiple countries. The wars themselves are usually started either for or because of True Runes, magical artifacts that impart immortality and great power. The protagonists of most of the entries recruit allies, the 108 Stars of Destiny, to their cause over the course of the game.
The Banshee is a random encounter in Suikoden.
The Ekidonna is a random encounter in Suikoden.
The Harpy is a boss in Suikoden II. It attacks by blasting the entire party with winds, or by picking up and dropping a single target.
The Mist Shade is a boss that attacks the party as they exit the swamps early in Suikoden II. It switches between male and female shapes as it casts magic, and is highly vulnerable to fire magic.
The Queen Ant is the first "boss" of Suikoden. The heros are tasked with clearing out the monsters of a local mountain, and find the Queen Ant at the bottom of the cave. She's almost invulnerable to their attacks, and can summon an infinite number of solider ants to defend herself, so defeating her is impossible. Realising this Ted unwraps his Soul Eater rune and sucks the Queen into a black hole. This leads to Ted's real identity being revealed, and kicks off the game's entire plot.
The Siren is a random encounter in Suikoden I & II. It can attack an entire row with its screams, and can occasionally cause berserk and unbalance.