Cleon
Legend
Updated. Finished?
I'd suggest applying the following tweaks to the Combat descriptions:
Beholder Pilot (Ex): A sentinel golem is normally inert, it only animates when a beholder or beholder-kin enters its helmet to operate it. A sentinel golem can hold a single beholder up to one size smaller than itself. While operating the golem the beholder pilot loses the use of its eye rays, which are used to power the golem. Powering the golem is as tiring as walking, so a beholder that operates a sentinel golem for longer than 8 hours must start making Fortitude saves every hour (DC 10, +2 per extra hour), taking 1d6 nonlethal damage per failure (see Forced March under Overland Movement).
Flight (Su): A beholder piloting a sentinel golem can render the golem's body supernaturally buoyant. This buoyancy allows it to fly at a speed of 20 feet. This buoyancy also grants it a permanent feather fall effect (as the spell) with personal range.
Tri-beams (Su): A beholder pilot can channel its eye rays through the sentinel's trident to produce a magical tri-beam once per round as a standard action. These three black beams of negative energy may be targeted at a single creature within 180 feet. A successful hit deals 6d6+3 points of negative energy damage (a successful Will save halves the damage). Additionally, a creature damaged by the tri-beam must succeed on a Fortitude save or fall unconscious for 1d4 rounds. The save DCs are equal to 10 + 1/2 sentinel's Hit Dice + Cha modifier of beholder pilot (18 + Cha modifier of beholder pilot for a typical sentinel).
I'd suggest boosting the Greater version's tri-beam attack damage to keep it in line with the trident damage. Adding "A Gargantuan sentinel golem's tri-beam attack does 9d6+3 damage." should be sufficient.
Do we want to include stats for a "Greater Sentinel Golem"?
Golem, Sentinel, Greater
Gargantuan Construct
Hit Dice: 24d10+60 (192 hp)
Initiative: -1
Speed: 20 ft. (4 squares), fly 20 ft. (perfect)
Armor Class: 30 (-4 size, -1 Dex, +25 natural), touch 5, flat-footed 30
Base Attack/Grapple: +18/+46
Attack: Trident +22 melee (4d6+24) or tri-beam +13 ranged touch (9d6+3 negative energy)
Full Attack: Trident +22/+17/+2 melee (4d6+24) or 3 tri-beams +13 ranged touch (9d6+3 negative energy)
Space/Reach: 20 ft./20 ft.
Special Attacks: Tri-beams
Special Qualities: All-around vision, construct traits, damage reduction 10/adamantine, darkvision 60 ft., flight, low-light vision, minor spell invulnerability
Saves: Fort +8, Ref +7, Will +8
Abilities: Str 43, Dex 9, Con —, Int —*, Wis 11*, Cha 1*
Challenge Rating: 15
Advancement: 25-48 (Gargantuan)