Serpent Sphere: This 6-inch diameter gold sphere typically has its command word inscribed somewhere on its surface.  When the command word is spoken, the sphere instantly affixes itself in space and time, becoming immovable.  No known force in the multiverse can harm the sphere once activated.  One round later, a small gate opens and 1d4+1 serpent heads emerge to attack any living creature in sight (including the triggerer, if within range).  The snakelike creatures have a maximum length of 10 feet; it is unclear whether they are separate creatures or the multiple heads of a hydralike monster.  In either case, the heads cannot detach from the sphere.  The serpent heads attack for 13 rounds before vanishing, along with the gold sphere.
Caster Level: 15th; Prerequisites: Craft Wondrous Item, summon monster VII; Market Price: 4,550 gp; Weight: 1 lb.

Serpent sphere heads (1d4+1): CR 2 x 2.3 advancement modifier; large animal (10 ft. long); HD 7d8+21; hp 54 each; Init +2 (Dex); Spd 20 ft.; AC 15 (-1 size, +2 Dex, +4 natural); Atks melee +11 (bite 1d4+7); Face/Reach 5 ft. by 10 ft./5 ft.; SA improved grab, constrict; SQ scent; AL N; SV Fort +8, Ref +7, Will +3; Str 25, Dex 15, Con 17, Int 1, Wis 12, Cha 2.
Skills: Listen +9, Spot +9 (other skills are unapplicable through the gate).
SA – improved grab (ex): If a bite attack hits, the serpent can constrict.
SA – constrict (ex): A successful grapple check (+16) causes 1d4+7 damage.
SQ – scent (ex): The serpent heads are able to detect creatures within 30 ft., 60 ft. if the creature is upwind, and 15 ft. if the creature is downwind.

Source: “Stairway of Desolation” in The Infinite Staircase
Converted by Kajal, the Southern Oracle