Summon weapons

Minions are summonable creatures that will fight for you (unlike pets). Minions as well as pets will follow the player, can pass through blocks when trying to catch up with player (but cannot while running around), cannot be damaged or killed, and last indefinitely until their buff is cancelled.

Minions can detect enemies before the player can see them on the screen, alerting you to incoming enemies. This can be useful when building and digging.

By default player can summon only one minion. The maximum amount of active minions that currently can be achieved with all equipment bonuses is eight. Minions can be combined. You are still only able to have one summoned light source and only one pet active at any time, regardless of the amount active minions you have.

Frost Hydra is a big exception since it cannot move at all, will disappear after a certain amount of time, and does not count towards the minion cap, while it still has summon damage type.

Armor
The following armor sets specifically affect Minions:

Accessories
The following accessories specifically affect Minions: