The Ancient Dragon will not spawn on its own. After the Tiki Totem has been defeated, Ruin Ghosts will spawn in the underground Ruins mini-biome and also spawn if there is a substantial amount of Clay Bricks in an area. Ruin Ghosts holding a lantern have a chance of dropping a Rusty Lantern, which can be used at a Ruin Altar to summon the Ancient Dragon.
The Ancient Dragon burrows through blocks while trying to reach the player. When it reaches 50% of its' health, each body segment can shear off when hit, turning into a Baby Dragon.
The Ancient Dragon charges towards the player.
The Ancient Dragon can inflict the Stoned debuff for 4 seconds when damages the player.
The Ancient Dragon can be summoned at any time of day.
It will burrow down offscreen and despawn when outside the Ruins.
For strategies on how to defeat the Ancient Dragon see Guide:Ancient Dragon Strategies.
Piercing weapons are highly effective, as damage on each body segment will be dealt to the Ancient Dragon's total HP.
Consider a Summon damage build, as your minions will still be active while you're petrified.
Unlike other worm-type enemies, the Ancient Dragon is knocked back when struck by player attacks, making the fight extremely simple if the player has any minions or weapons that attack quickly