God Wars is one of the most difficult clan activities in Runescape. It is especially hard to get a hilt drop from the two beasts at God Wars, let alone an Armadyl hilt drop from Karee. Here is a list of the basic requirements one should have before even thinking about heading out to participate in this difficult activity.
1) Combat level 100+
2) 90+ Hitpoints
3) 90+ Range (ideally 99 to kill it fast)
4) 70+ Defense
5) 1-5 million GB (to buy supplies and armor)
6) A clan of 3-5 people
With these requirements, or better, you should be set to head out and fight Karee.
Proper Armour is the most important part of going to Armadyl to fight Karee. There are several different types of armour you can take, but the best setup would start with a Verac's plateskirt, Karil's leather top, and either an Armadyl Helmet or a Dhorak's helmet. (Hint: the reason you need 70 defence is to wear the Barrows items just mentioned.) Which helmet you need to take depends on if you have an Armadyl pendant or not. This can be obtained from a quest, but most likely you will need to get an armadyl helmet as the quest is difficult to finish.
(A piece of Armadyl is needed to get into the Arena. This is why you need the helmet or the pendant.)
You will need two sets of boots: climbing boots and dragon boots. The climbing boots are used to travel over the obstacles to get to the arena and the dragon boots are necessary to fight the beast. You also need a Zamarock item. If you have a full Zamarock book, then that will do just fine. If you don't, just buy a Zamarock helmet. This Zamarock item is needed for when you are obtaining the necessary kill count to get into the arena, which will prevent many of the Zamarcok monsters from attacking you. When you are done fulfilling the kill count, have a Obby shield for extra protection. For a cape, use Ava's accumulator, which will automatically retrieve your bolts. Finally, grad a Fury amulet for your necklace and a ring of life, just in case you die.
Your weapon of choice is the rune crossbow with Ruby (e) and Diamond (e) bolts. (I will explain why you need both later; however these are both used for combat against Karee.) Grab about 100 emerald (e) bolts to get kill count with. You can use diamond (e) if you want, but you can get emeralds to save money.