The Souleater - one of my favorites.First of all, what level are you?
Do you have the Light Sword, Ivory Blade or Cane Corpus with a Fairy Ninja to handle it ?
Do you have canned elementals or several spellcasters who can cast it ?
Do you check radar for "other monsters" who will join the fight with Souleater, or do you just charge around the corner with search turned on ?
Souleater is easy to kill if you are prepared. Use radar and wait for the wandering monsters to wander off. Hide in the little space behind the rock south of Souleater. Attack any monsters that wander by and level up a few players. Equip your people with Medusa Stones and Mystic Arrows - this is the monster you have saved them for. If a player has throwing skill and cannot cast Summon Elemental, give them a canned elemental. TURN OFF SEARCH MODE so you don't lose a turn.
Approach Souleater slowly, hug the left side of the rock wall. Click on the sword (attack mode) just before it sees you. Sometimes it will hear you and move toward you - watch radar carefully. Click on Walk. Cast elementals to your right and slightly ahead of you. Have someone (your slowest spellcasters) cast element shield and soul shield. Start combat, move forward just enough to target Souleater with arrows & rocks. Let the first round finish. If you are lucky you will have a wall of elementals to your right, they will be covered with soul & element shields and Souleater will have no chance to move into slapping range.
For round two, WALK BACK A LITTLE. Cast a haste spell and have everyone with rocks and arrows start a long-range attack on Souleater. The elementals will hopefully form a meat shield and will beat each other up when they get crazy or turncoated. The spellcasters who cast element and soul shields last turn should cast elementals now. They will appear after "the slapping" and should protect you from your turncoated/insane elementals. Or cast sane mind on your elementals/players.
Maintain the long range attack for a round or two. Start each round with a walk in case Souleater is not distracted by the elementals. Then move in for 1-2 rounds of sword swinging and stick poking.
The Djinn of the Clouds are also easy. Even though they have high air-spell protection, a Death Bomb will usually kill one per bomb. Start combat, move up, drop an elemental, throw a death bomb then run away.