
I admit it’s been awhile since I’ve watched any Ben 10, but for the purposes of stating out a rough adaptation of Ben’s original Omnimatrix, I think I’ve got a clear idea of how it is supposed to work.
And thanks to Alien Archive 2 we have a clear polymorph rules with which to do it!
Omnimatrix level 20
priceless
bulk L
The omnimatrix is a hybrid item worn on the wrist, and re-sizes to the wearer. There is a brief bonding process, and the omnimatrix may be keyed to a specific individual’s genetic code, such that only that individual or a close relative may bond with the device. Once bonded, as a standard action the wearer can activate the omnimatrix to transform into one of the stored polymorph forms within the device. This effect lasts for one minute, after which the omnimatrix must recharge for five minutes.
Upon discovery, the omnimatrix has the following three forms unlocked, but more may be unlocked at a later date, at the GM’s discretion. Further abilities of the omnimatrix – capture mode, hybrid forms, etc, are also left to the GM’s discretion.
The forms below are provided as 4th-level Polymorph Forms, but as the wearer grows in level, can be increased to 5th and 6th-level Polymorph Forms at the GM’s discretion.

TETRAMAND FORM (aka Four Arms)
Large
DEFENSE
DR 5/magic
OFFENSE
Melee slam
SPECIAL ABILITIES
Four Armed (Ex) Tetramand have four arms, which allows them to wield and hold up to four hands’ worth of weapons and equipment. While their multiple arms increase the number of items they can have at the ready, it doesn’t increase the number of attacks they can make during combat.
Powerful Frame (Ex) Tetramand are built for strength and gain a +4 morale bonus to Athletics, Intimidate, and all strength checks. When determining what bulk they can carry, consider their strength score to be 6 points higher than it is.

PYRONITE FORM (aka Heatblast)
Medium
Senses darkvision 60 ft, low-light vision
DEFENSE
DR 5/–; Immunities fire
Weaknesses vulnerable to cold
OFFENSE
Melee slam (damage is half blunt, half fire, targets EAC)
Spell-Like Abilities (CL 8th)
1/day explosive blast
3/day overheat
At will – energy ray (fire only)
SPECIAL ABILITIES
Burning Accuracy (Ex) Pyronite have an inborn gift for throwing fire and gain a unique weapon specialization with their energy ray that adds 1-1/2 × CR or character level to damage.

KINECELERAN FORM (aka XLR8)
Medium
Senses low-light vision
OFFENSE
Speed 90ft
SPECIAL ABILITIES
Genetic Momentum (Ex) Kineceleran are built for speed, and may increase their speed by 20ft on any move action that is in a straight line. Alternatively, as part of a move action in a single direction, they may move up to 20ft of their movement on a horizontal surface, so long as they end the movement on a flat square. When running they move at six times their speed (instead of the normal four).
Hyper (Ex) Once per day, a kineceleran can take an extra move action
Prehensile Tail (Ex) A kineceleran’s tail is as effective as a hand at manipulating objects, which allows them to wield and hold up to three hands’ worth of weapons and equipment. This does not increase the number of attacks they can make during combat.
Note for GMs – The omnimatrix as presented here is effectively an artifact, which is why it is a level 20 item and the price is listed as priceless. This is particularly true if you add in the later abilities and forms as seen in the various Ben 10 shows. Use caution when adding this to your game.
Jeremy Corff
Artist and Writer