Most characters in Ground Zero have one or more special abilities which could be called 'mutations'. Each mutant represents a unique combination of beneficial and detrimental mutations, and thus must be generated from scratch.
The player decides how to distribute their character's mutant perks and flaws, based on their genotype. Mutations are determined through a guided randomization method - all mutations are rolled randomly, but the player may reroll the results by spending BPs.
With the GM's permission, players may create characters using the more advanced Complete Mutant rules.
All mutations are classified as either mutant perks or mutant flaws. Perks are beneficial, while flaws are baneful. Every mutant will possess one or more from each category.
Not all mutations are equal; perks and flaws are broken down into minor, medium, and major categories. Mutations from different categories have different BP values. Major mutant perks cost 6 BPs each, medium mutant perks cost 4 BPs each, and minor mutant perks cost 2 BPs each. Conversely, major mutant flaws grant 6 BPs, medium mutant flaws grant 4 BPs, and minor mutant flaws grant 2 BPs. Based on how you choose to distribute your BPs, you can choose whether you have a lot of minor mutations or just a few major ones.A character's mutations are determined by rolling d% on the random mutant perks and random mutant flaws tables. Mutant perks and flaws are determined independently. Decide how many mutations of which level your character possesses, and roll that many times on the appropriate column for your perks and flaws.
(Some mutations - denoted in the tables by the superscript Psi - are psionic in nature. See the Psionics page for details on how these powers work in Ground Zero.)
Near-humans will spend 2 to 4 BPs on mutant perks, and get a similar number from mutant flaws. A few more BPs might have to be spent on rerolls. Mutant humans will usually spend at least 12 to 18 BPs on mutant perks, and get about half that back in mutant flaws. Remember - a mutant human needs to have at least as many BPs worth of flaws as his highest-cost perk.
If you don't like a perk or flaw that you've gotten, you can spend BPs and roll again. It costs 1 BP to reroll a minor perk or flaw, 2 BPs to reroll a medium perk or flaw, and 3 BPs to reroll a major perk or flaw. You can roll more than once for the same mutation, as long as you have the BPs. You can also choose to sacrifice attribute points or take on additional flaws to gain BPs, if you're that desperate. Usually it's not worthwhile to reroll unless you've truly been shafted by the dice.
In general, mutations of different types stack, so you can have Thick Fur (granting +2 natural armour) over your Scaly Armour (+4 natural armour) for a total of +6 to Defense. Lucky mutant. If you roll a combination that makes no sense, you must roll again for a different mutation. (However, the GM always gets the final say on this.)
As you may have noticed from the tables, most mutations also possess more extreme versions. The base-level mutation is the regular version of the perk or flaw. Most perks and flaws can be advanced, with a maximum of two advancements; if a mutation is rolled more than once, simply advance it the appropriate number of times. (If the mutation cannot be advanced, then reroll instead).
Mutants can also select special mutant talents in place of regular class talents. Several of these will allow a mutant perk to be advanced in power, or a mutant flaw to be reduced in severity. Other mutant talents allow mutations to be used or modified in other ways. See the Skills & Talents page for more details.
Many of the mutations listed here come with physical deformities. Some mutations are easy to hide, while others are harder to conceal.
Any mutation that alters a creature's physical appearance imposes a penalty on the creature's disguise-based Bluff checks. For creatures trying to conceal multiple deformities or alterations, the penalties stack. In general, a minor mutation imposes a -1 penalty on disguise-based Bluff checks, a medium mutation imposes a -2 penalty, and each major perk or flaw imoposes a -3 penalty.
The GM may adjust these penalties depending on the specific mutation in question.