Mud

Location
Mud is located in the Gabomba Catacombs. To reach it, in the first grass-covered room you climb down into, go up so that you're in the semi-enclosed area between rocks below the mass of grass just to the left of the elevated area you climb down from. Cast Cyclone here and you will automatically be transported through a "cyclone ground portal" hidden within the leaves above, and you will be dropped into the floor below right next to Mud's position. Save, then battle Mud to earn out.

As an opponent
Statistically, Mud has 500 HP, 44 PP, 153 Attack, 41 Defense, 122 Agility, and 15 Luck. Like all other Venus Djinn that are fought, in terms of resistance, it has a Venus Resistance rating of 193, Mercury and Mars Resistance ratings of 100 each, and a Jupiter Resistance rating of 25, and in regards to its abilities it uses its available Venus-based attacks with a Venus power rating of 125.

Mud can use the following battle commands:
 * Briar: Used 53 out of 256 times, this is a Psynergy spell that causes a series of quite large spiked vines to grow out of the ground quickly to assault the opposition, dealing a Venus-based attack with a power rating of 70 and a range of 3. This ability consumes 11 of its user's PP.
 * Quake Sphere: Used 47 out of 256 times, this is a Psynergy spell that prompts three rectangular sections of ground underneath the party to jolt upward and retract into the ground quickly thrice in succession, bouncing each Adept three times, dealing a Veus-based attack with a power rating of 65 and a range of 7. This ability consumes 15 of its user's PP.
 * Mad Growth: Used 41 out of 256 times, this is a Psynergy spell that causes a group of thorny vines to erupt from the ground and through the Adepts for a short time, dealing a Venus-based attack with a power rating of 60 and a range of 3. This ability consumes 10 of its user's PP.
 * Gaia: Used 35 out of 256 times, this is a Psynergy spell that causes the ground beneath the enemy to open up and engulf the party in a wide reverse shower of Venus energy and medium-sized boulders, dealing a Venus-based attack with a power rating of 40 and a range of 3. This ability consumes 7 of its user's PP.
 * Spire: Used 29 out of 256 times, this is a Psynergy spell that causes a thick stalactite to fall out of the sky and shatter onto a target, dealing a Venus-based attack with a power rating of 40. This ability consumes 5 of its user's PP.
 * Attack: Used 28 out of 256 times, this is this monster's standard physical attack, but for this monster it is counted as a Venus-based attack rather than a non-elemental attack.
 * Flee: Ued 23 out of 256 times, this enemy has the ability to attempt to Flee the battle, thereby ending the battle if successful without rewarding you with the associated EXP, Coins, and the Djinni itself.

When defeated, Mud yields 360 EXP and 358 Coins, and the Mud Djinni is added to your party's Djinn collection. If you fell it with an offensive Jupiter Djinni like Waft, its rewards increase to 468 EXP and 465 Coins.

It is possible to have four Jupiter Djinn in your collection at this point, so having Summon summon Thor with them will deal over 400 damage to Mud in one blow (over 440 if she is equipped with the Clarity Circlet, meaning you only need at most two more actions to KO it in the first turn.

Description
When Set, it increases base HP by 10, base PP by 4, and base Agility by 3.

When Mud's battle effect is used, the user lobs mounds of orange mud at the positions of each member of the enemy party. All enemies' agility ratings are temporarily lowered down to 50%, the lowest value the Agility rating can be debuffed down to. This is identical to the effect of the Venus Djinni Vine in The Lost Age.

Ability analysis
In various viewpoints, halving all enemies' agility ratings is equivalent to doubling all party members' agility ratings with Djinn like Coal. And as a matter of fact, halving the enemy's agility does have one situational advantage over the alternative: because it does not count as a buff to your party, if the enemy is a boss with the Break Psynergy, it cannot negate the agility disadvantage before the normal timer for the effect runs out naturally. Mud works against bosses like Dullahan, who ordinarily remove all buffs you cast upon yourself with Break but do not have any specific measures to remove negative effects from themselves. So, depending on your party setup and battling approach, Mud can be very useful. When Isaac's party joins Felix's party along with their returning Djinn late in The Lost Age, the Venus Djinni Vine returns along with them to serve as an identical copy of Mud. The two Djinn are usable interchangeably for the same situational purposes.

Name Origin
Mud is the end result of water mixing with dirt. The name makes sense seeing as how mud (both the Djinni and the substance) can slow down your enemy.