This command changes whether or not an NPC (your target) will be damaged by hits from you.
sifh [0 / 1] Target Command
| 0 / 1 | Specify '1' (without quotes) to make your targeted NPC not take damage from your attacks. Specify '0' (without quotes) to make your targeted NPC be damaged by hits from you. |
sifh 1
The above command would make your currently targeted NPC be unaffected by any hits from you.
sifh 0
The above command would make your currently targeted NPC be damaged by your attacks.