Flame Plate
From Pixelmon Wiki
A Flame Plate is a held item that raises the power of the holder's Fire-type moves by 20%. When held by Arceus, its typing and its signature move Judgment become Fire-type, and it and any Fire-type move receive the power boost.
It can be obtained as a drop from legendary boss Pokémon and from Beast Chests. It can also be found in Desert Temple and Nether Fortress chests.