First off:
But yes, that's right, if you're up close and personal to a xeno and it takes damage, there's a chance it will splatter its blood all over you, doing random but significant amounts of burn damage to one or, rarely, more body parts. It's possible even to get your face melted completely off, so, uh.
The way it works is: Whenever a xeno takes damage from any source, it checks to see if there's blood spatter. This chance is modified by several things, including the source of the damage (sharp/pierce weapons give a large chance), the type of damage (brute vs. burn gives a higher chance), and which body part (if any) is being targeted. If successful, the floor will get a spatter like normal, and any adjacent humans (or species) within 2 tiles will have their own chance of getting splattered with it -- this chance is also modified by a lot of stuff, including distance (on the same tile? VERY high chance, 1 tile: moderate, 2 tiles, low chance), and number of people that have already been splashed.
If you get acid on you, it REALLY hurts, though it's not likely to kill you unless you take some extremely serious burns to the head or chest; burn damage does not cause bleeding so you will not bleed out or break limbs.
Second,
Xenos now get two special attacks: BITE and TAIL.
Bite attacks kick in randomly when you claw at a human (or species) target; think of it as a 'critical hit'. It deals damage based on your normal melee damage plus a very significant bonus. That's pretty much all there is to it. Different castes have different chances of it kicking in.
Prepare Tail Attack is a verb in the alien panel for all xenos except larva. Both preparing and "holding" a tail attack costs initial plasma and a small amount of plasma per tick, in addition you will not regen plasma even on weeds while your tail is ready for an attack, it takes a lot of musclepower to keep it coiled up. When you next make a harm-intent attack, you will unleash the tail strike and deal damage based on how long you've kept it ready, up to about 15-20 pulses (it gives a message when you've maxed out). The tail damage ranges from fairly low for a quick strike to extremely heavy for a maxed-out tail strike, potentially enough to kill a marine and certainly enough to shred unprotected body parts. Hunters get a speed bonus, they max out their tail charge faster than any other caste, and Queens get a small damage bonus. You can "unready" your tail attack at any time just by clicking on the verb again.
Third,
Queens can now toggle between 3 different harm-intent states -- "forbidden", "restricted", and "allowed". The first completely halts any claw attacks whatsoever - you will hesitate and just not attack. It is the default on round start, so you need a Queen if you want to harm survivors. The second allows you to claw, but you deal HALF damage - it's intended to let Queens give an order to "harm only if you REALLY need to". The third has no restrictions, and should a living Queen die, "harm allowed" is automatically enabled if it wasn't already.
Fourth,
Xenos are no longer able to drag-drop people in order to access their inventories. This means no taking off ANY gear. Sorry xenos! To compensate, however, the resist time on nests has been DOUBLED, meaning there's a significant risk that the prey can burst without ever even being able to escape. Sorry marines! Another note -- a new timer has been added to stop re-buckling. If you unbuckle someone from a nest, they will not be able to be rebuckled for around 20 seconds.
Any comments or questions are welcome!