Strains are variations of the xenomorph you play as, changing up their play style to something either slightly or completely different to the normal xenomorph. This allows you to change your play style to experiment with.
You can pick your strain from the get go if your caste has any strains available to them. When you evolve you will lose the strain you previously picked. Each Xeno can purchase one Strain available to their caste and they are permanent.
Under the Alien tab you can buy strains for yourself with the Purchase Strains verb.
Each Strain is permanent, will alter how you'll play the caste and can not be reverted.
Trade the ability to tail sweep for the ability to use headbutt while your crest is lowered. Additionally, your headbutt does more damage, gains 1 tile extra range and you're able to move slowly while fortified.
Trade the ability to fling and lunge for a lower cool down, increased damage and range on your punch ability. Punch loses the ability to immediately break bones. Gain a new ability, Jab: A stun ability that applies no damage but refreshes punch ability.
Trade the ability to spit/spray acid and a hefty chunk of your armor for greatly increased speed and three new abilities: Impale, Dodge, and Tail trip. Dodge is an active ability that greatly buffs your speed and allows you to phase past tall hosts. Tail trip is also an active ability that trips your target, causing a daze and if they are tagged, a short knockdown. Impale deals direct damage and if they've been tagged, stab them twice.
Trade most of your speed to become a nigh-indestructible bulwark of the Queen. Your slashes deal increased damage to prone targets, and you gain a stomp that knocks over opponents in front of you as well as a ability that buffs your next slash and one that knocks your opponents back.
Trade your corrosive acid to get a shield that perfectly blocks one attack, which recharges out of combat. Gain the ability to use pierce that penetrates through opponents, also instantly recharging your shield. You also gain cleave, which has two states: Root, which'll immobilise a target; Fling, which'll fling a target away from you
Trade your base abilities for increased health, mobility and new abilities that turn you into a immobile death machine. Build up your rage levels through slashes and unleash terror upon thy foe with your new abilities. Apprehend allows you to close the distance between you and your target. Clothesline allows you to deal moderate damage to a target next to you in exchange for using a level of rage. Annihilate your targets all around you with the new eviscerate ability to rip and tear your enemies guts out.
Trade your base abilities and plasma for a shrapnel based powers. Gain shards of spikes passively or when you get hit. Gain 3 new abilities to replace the old ones. Spike Shield allows you to gain a temporary shield that, when damaged, sprays shards of shrapnel outwards. Fire Spikes allows you to launch spikes in the a desired direction. Spike shed allows you to shed all your spikes, launching them all around you, for a quick boost in speed.