Tower
Tower markers indicate an attack that will do damage to anyone standing inside of it. If there are not enough players inside a tower to take the attack, the tower explodes and deals a high amount of party-wide damage. Unlike stack markers, the damage done by towers is usually not split between players.
There are many variations of towers with non-standard visual indicators in the game. They are typically indicated by a small, stationary, circular glyph on the ground, but often have a tower-like structure inside them.
As towers explode for often-fatal amounts of party-wide damage if empty, it is still advantageous to have a player stand in a tower that would defeat them in order to protect the rest of their party.
Types
Standard Tower
This tower deals varying amounts of damage and simply requires one player to stand inside. Often can be handled by any role.
Some older high-end duties may require tanks to handle towers despite a lack of unique marker.
Tank Tower
This tower usually combines the visual indicator for a tankbuster with the tower itself. It requires one player and deals a very high amount of damage, usually only allowing a tank to survive the attack.
Some older high-end duties do not display the tankbuster indicator on tank towers.
Multi-player Tower
This tower usually has a visual indicator showing how many people are required to prevent the tower from exploding. Common indicators are small circles on the ground or tower-like structures appearing multiple times inside the marker. Some tower indicators visually react when a player steps inside of it.
Multi-player towers may also be paired with a stack marker, indicating that damage will be split between all players in the tower.
Summoning Circle
These are single or multi-player towers that will disappear as soon as the requisite number of players stand inside. Unlike regular towers, which require those inside to wait, Summoning Circles can be left the instant their conditions are met.