The Current State of Affairs: Karosos

Karosos is a Blue Slaad. He is vile, hateful, and grim. He has also figured out how to implant slaad pellets as red slaad do. This makes him a truly dangerous foe, especially in a fight of attrition. Those who don't know what to look for after fighting him may find themselves suddenly giving birth to more enemies.
However, in the arena, Karosos makes sure to not implant eggs, or, if he does, he makes sure to have them extracted. He has no desire to see more slaads enter this world. He believes that one, himself, is enough. Any more will just get in the way of his eventual transformation into a Death Slaad.

Karosos Blue Slaad Slaad Brooder 1 CR 10

Init +3    Senses S/L +10/+10 Darkvision   Languages: Common, Chaotic

Defenses AC 25 (+3 dex, + 9 nat, -1 size, +3 arm) Will +7   Ref +9   Fort +16

HP 106 (9d8+72)  Fast Healing 5 Immune: Sonic Resist acid, cold, electricity, fire 5

Speed 30 ft

Melee:

• Claw +16 (2d6+8)
• 4 Claws +16 (2d6+8)  and  Bite +16 (2d8+4)

Base attack +9     grp +21

Abilities   STR 26  DEX 16  CON 26  INT 4  WIS 8  CHA 8

Feats: Multiattack, Improved Multiattack, Great Fortitude, Ability Focus (Implant)

Skills: Climb +19, Hide +10, Jump +19, Listen +10, Move Silently +14, Spot +10

Equipment: Plane Shifter (as spell, 2/day), Bracers of armour +3

SLA:

• At will: hold person (DC 12), passwall, telekinesis (DC 14)
• 1/day: chaos hammer (DC 13)
• Summon Slaad: 1/day, 40% chance of success to summon another blue slaad.

Implant:

• Fort DC 27 negates. Any natural attack can implant a pellet. If not treated within a week, the host dies. See Red Slaad’s Implant ability, MM 229

Disease:

• Fort DC 22 negates. Any natural attack can deliver this disease. Incubation period is one day, 1d3 dex and 1d3 cha damage.

Improved Grab

• When Karosos succeeds one or more claw attacks, he may attempt to start a grapple. Each successful grapple check during successive rounds deals bite damage (2d8+4)

Slaad Brooder is a prestige class from Savage Species, which is where he gets his Implant ability.
He has only two items, the bracers of armour and the item that grants Plane Shifting abilities. He does not plane shift away if a gladiator fights goes against him, but should be encountered in a real combat situation, he has no qualms about plane shifting out should things go poorly.
He generally prefers to mix things up in melee, tearing his opponents apart. While it may be optimal to spread his attacks out among multiple people to hit them all with Implant, he prefers to down one enemy before moving to the next. Once he engages someone in melee he does not like to move, preferring to make full attacks.