"The Gravite two-handed sword is a melee weapon released with the Dungeoneering update.
Like all Gravite weapons, it requires 45 attack to wield (with 45 Dungeoneering). It will also serve as a knock-out weapon for many Activities.
This item cannot be created by Smithing. It can only be bought as a Dungeoneering reward, costing 40k tokens.
It is currently the strongest weapon for nonmembers, with an 87 crush bonus and a 90 strength bonus. Now the maximum strength bonus a nonmember player can have is 102 with a Strength Amulet, Rune Gauntlets and Gravite Two-Handed Sword. Theoretically, the maximum hit it can do in a free to play world is 393 damage.
Various websites show up with different results with some as high as 407.03.
However the weapon only lasts for 10 hours in combat (like all other Gravite weapons). After these 10 hours of combat it will become completely uncharged and will have (broken) after its name.
To recharge the weapon you must go to the reward seller in Daemonheim. The recharge cost is 1 million gp (for a completely uncharged weapon) or 100,000gp with 6,500 tokens. This weapon has the same attack speed as a rune Battleaxe."
Taken from runescape.wikia.com
So I guess the down side of it is the cost of tokens, and that it degrades.
