Those towers are added by Thaumcraft.
As was also mentioned you can do the ic2 (expensive) recipe to make glowstone, or if you're lucky you might have a priest villager that you can trade emeralds with to get glowstone.
While I haven't gotten a feather to see how good feather-fletching is yet, I would suggest a slime farm to get slime fletching and rods for arrows. The slime fletching gives the arrows 96% (maybe more, don't remember off the top of my head) accuracy (leaf fletching is something like 87%) and the slime rods make the arrows lighter than wooden ones. From there you can make a bow and with TC3 enchanted bowstring. The enchanted bowstring decreases the time to pull back the bow and adds an extra modifier, and while slime bows are slightly slower (.2 seconds) than a wooden bow they also have nearly 7x the durability.
Basically, with TiC slimes are your friend, and make plenty of arrows and a good bow. You'll save yourself a lot of trouble later in dealing with some of the mobs.
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With the zombie awareness mob, they actively try and path find to you. One small hole in your defenses, and they'll find it. Combined with extra types of creepers from Primitive mobs, and the odd rare occasional mob that can shoot fireballs from Internal Mobs, if there isn't a hole, they could soon make one....
(If you can find trees, that is)
