The demon spear is a mower in the blade class of mow my lawn default shop. It is currently the most expensive bladed weapon. The demon spear is a very long-reaching weapon. The part of the demon spear that breaks objects (and mows grass) is the part at the end that splits into two separate blades. The demon spear is very useful in PvP, as it has one of the longest reaches in the game.
The demon spear costs 900 Quintilian trimmings, and can be bought in the default MML shop in the "blades" category.
Buying the demon spear will give you the "Stop copying my build." badge.
Each part broken with the demon spear nets 999,999,999,999,999,999 trimmings for the user. The demon spear also has a 1 in 750 chance to give a single player point to the user from the budget. This may seem like not a lot, but with the frequency of the running of the script, points become common.
The demon spear has no special ability besides insane reach.
The demon spear is a reference to the Dark Souls weapon of the same name. Both weapons have long reach, and thus are good in PvP situations. The badge you obtain from buying the demon spear is a reference to the Mask Of the Child, another Dark Souls item.