Terraria (Wiki): Cobalt Naginata

The Cobalt Naginata is an Ore Spear that pierces enemies and an alternative ore counterpart for the Palladium Pike. 

A Cobalt Naginata cannot autoswing. Its attack reaches 11 tiles in radius. At an optimal distance, the Cobalt Naginata can pierce five enemies. However, multiple bodies will be damaged should they all line up for the player.

When normally used, the Cobalt Naginata will not emit light, and attacks do not go through walls. It has the weakest knockback, lowest base damage, and slowest use time among Ore Spears. 

In addition to having slightly better stats, The Dark Lance is also somewhat accessible in Pre-Hardmode, making it a viable alternative. The Cobalt Naginata, however, has a slightly greater range (3DS, old-gen consoles).

Combat-wise, all Flask items will imbue their unique effects since the Cobalt Naginata is a melee weapon.

The Cobalt Naginata is best modified with Godly or Demonic for overall stats improvement. Both modifiers equally increase the average damage output.