Aura must be valued at 137g for Abyssal Scepter to be gold efficient.
Abyssal Scepter's aura can be helpful in a variety of situations, not all of which are immediately obvious. It is especially powerful for melee champions and short-ranged casters, who are exceptional at close combat to the enemy and deal considerable amounts of magic damage. With proper maneuvering, these characters can apply the debuff to the entire enemy team at once, securing kills for longer-ranged champions.
The icon indicating the debuff aura often appears before the enemy who carries it. If an enemy is standing in a nearby brush or just over a wall, the debuff icon may give them away even if they cannot be seen.
The following champions are classified as mid-ranged casters, or feature core mechanics that place them within a moderate range of the enemy. These are not intended users of the item, but many can easily make use of the item:
Sunfire Cape - fully fits within aura range, nice item pair to greatly improve one's overall survivability and aoe damage output.
Hextech Gunblade - active part has range of 700 units. For best results, try to make sure that the missile hits a target within the aura radius, an applied slow also helps to keep target in aura range.
Deathfire Grasp - active part has range of 750 units. For maximum effect try to hit targets within the aura radius.