The 0.9 patch to They Are Billions added two things: a new difficulty setting (max population), and a new Special Infected, the Giant.
The difficulty setting is a new population setting. The previous population choices were few, very low, low, medium, and high. This new choice, max, comes on the high end. The result is a new set of hard challenges, pushing the maximum score factor up to 800%. Of course, this doesn’t affect any existing games, as you only choose difficulty at the start of a new game.
I’m currently working my way through a 160% difficulty game (80, low, Peaceful Lowlands) so I can’t really comment on the new difficulties. Higher population means both more Infected on the map at the start of the map, and also larger swarms. Do note that the difference in score factor between Medium and Max is just under 3x, greater than the gap between the “easiest” map and the “hardest” (in quotes because some people find certain challenges easier or harder than the devs intended). I haven’t yet watched any >500% videos on Youtube yet, although AznElite123 uploaded a win at 800% just nine hours ago.
The other major feature in the 0.9 patch is the Infected Giant. The giant(s) appear at the start of the game and roam around the edge of the map. You won’t see them unless you set the difficulty to Challenging or above (um, what score factor is that? or is it just based on pop?), and if you do have one in your game, you’ll see Giants as an icon on your minimap — even if you don’t have visibility into the area. Don’t see an icon? Then you’re safe, your game won’t have any giants. Just, you know, tens of thousands of other infected…
The Giant has a huge amount of hitpoints, a long range, and has an area-of-effect attack that even damages other infected. He’s big, he’s dumb, and he’s deaf — which means noise won’t draw him out. The only way to engage him is to hit him with weapons, but then look out — nothing will stop him until he’s killed anyone that’s pissed him off. You don’t really want to get static defenses (like ballistas, shocking towers, or executors) involved here, as the giant’s huge hitpoint pool and armor suggests that he’ll take out defenses before he dies. The most cost-effective troop to use would be snipers (although they move incredibly slowly!) followed closely by soldiers. A Titan is, of course, the most threatening single unit, but they’re far far more expensive than anything else. Maybe I’ll see this guy in my next game?
There were a couple other changes in the patch. For one, they reworked armor. The next result is that units with weak attacks (rangers, weak infected) now do slightly more damage against armored units (soldiers, titans, runners, & special infected) while strongly-armored units (soldiers, titan, chubbies) stand up better against strong attacks (snipers, thanatos, ballistae, executors).
There were some other combat changes. Soldiers and Titans now do more damage, and Veteran Soldiers and Rangers have a greater attack range (over non-veteran units). This last change is new; previously, becoming veteran only increased damage and attack rate. Now, veteran units will be even more effective behind walls (or in the back of your formation) due to the higher range.
The devs actually added a quite-substantial post about the patch, including the giant, and that’s where I’m pulling my information from. Check it out on the steam forums.