The Proto Deathmask is an enemy in Final Fantasy IV: The After Years.
While Reflect can be a nuisance to the party, Proto Deathmask is not difficult to defeat as it can only hit one character at a time. Reflect Slow off of a party member or use a Spider's Silk to slow it, preferably Slow since Spider's Silk are harder to get at this point, and either bounce Flare spells off party members or use Quake for black mages (or Leviathan or Bahamut if using Rydia), while fighters just use their regular attacks. If the player brought Edward with the Apollo Harp or Loki's Lute, or Cid or Luca with a powerful hammer such as the Sledgehammer, they will be of great use against the foe.
Proto- is a Greek prefix that means "first."