Desolation Wurm

Using the worm in the desolation has a few mechanics. Depending on what weapon you use, each has a different effect in the worm. It's worth reading through the Main Wiki Wurm Entry to fully understand how the Wurm works.

Because the Desolation is full of undead, using a Holy Damage weapon is a good way to get double damage with auto attacks. You can get a 9 smiting prayers holy weapon at Luven Underwood for 5 Minotaur Horns (farmable in the entrance of Elona Reach)

Spears are ideal for everything else due to their high damage + ranged attack.

Scythes in some scenarios can allow you to hit multiple targets at a time but due to killing groups being a bit 'situational' in solo play, are a weaker option than a spear.