1. The souls of wicked men who have died (Greeks).
2. Spirits of a pre-Adamic race.
3. Offspring of the fallen angels and the women before the flood (Gen. 6:1-4).
4. Those angels who followed Satan at his fall (biblical position).
Characteristics of demons:
1. Spirit beings (Matt. 17:18, cp to Mark 9:25).
2. Know Jesus Christ (Mark 1:24).
3. Know their own end (Matt. 8:29).
4. Know the plan of salvation (James 2:19).
5. Have a system of doctrine (I Tim. 4:1-3).
6. Immoral, wicked, unclean (I Tim. 4:1-3).
Activities of demons:
1. In general:
a. Attempt to thwart the work of God (Rev. 16:13-16 and Daniel 10:11-14).
b. Extend the authority of Satan (Eph. 6:11,12).
c. Demons may be used by God in carrying out His purpose (II Cor. 12:7; I Tim. 1:19; I Cor. 5:5 and I Sam. 16:14).
2. Some particulars:
a. Can inflict disease (Matt. 9:33).
b. Can possess humans (Matt. 4:24).
c. Can possess animals (Mark 5:13).
d. Spread false doctrine (I Tim. 4).
e. Oppose the spiritual growth of God's children (Eph. 6:12).
Destiny of demons:
1. Temporarily some are confined. For instance, some who were free during the lifetime of Christ were cast into the abyss (Luke 8:31) and will be loosed to do their work during the coming tribulation days (Rev. 9:1-11 and 16:13-14).
2. Eventually all demons will be cast with Satan into the Lake of Fire forever (Matt. 25:41 and Rev. 20:10).