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Every 50th kill of this enemy drops Ghost Banner.three ways to meet one
They belong to the halloween season, when they start appearing down in the caverns of their own accord. A graveyard changes that. Put enough Tombstones together to form the mini biome and ghosts turn up there around the clock, on the surface as readily as underground. The third route is the one that catches people out: breaking a tombstone can produce one on the spot.
smashing graves
The roll happens as the grave breaks, and one of three things has to be true for it to count: it is night, you are standing in a graveyard, or the stone was buried below the surface layer. Only two ghosts can be active at once, so a mass clear-out will not bury you. The odds roughly double with each step up in world difficulty, from a small chance in a classic world to a coin flip in master.
If the game cannot find suitable ground off-screen, it places the ghost on-screen instead, which can mean directly beside you. Do not stand in the middle of your own death pile while you clear it. This route also ignores the enemy spawn slider completely, so a journey world set to zero spawns still produces ghosts out of broken graves.
the natural spawn is fussy
Underground they will not appear if a town NPC is nearby, if you are standing in front of walls that count as safe housing, or if you have been idle for the last few seconds. Idle is generous here, since holding a movement key against a wall counts as moving. A Shadow Candle throws all of those conditions out and lets them spawn regardless, which is how you farm them on purpose.
how they move
They drift rather than walk and they pass straight through terrain, so a wall is not cover. One quirk is worth exploiting: to gain height they need solid blocks to travel through. With nothing but open air between you and the ground, they hang low and never climb. A platform out in open space is close to free.
fighting them
Melee reaches them through walls here, which it normally cannot do. A Spear manages it and so do whips, and both cover enough area to handle a crowd, which is what a graveyard eventually hands you. On classic difficulty they will also pick up coins you have dropped, so the one that looted your death pile is worth chasing down. In current versions a ghost raised from a grave fixates on whoever it spawned near and tries to flee once that target is dead.