Core Keeper 1.3 minions no longer expire on a timer. Start with a summoning tome, use it to bring out your group, then choose equipment around minion capacity and the mana your summons reserve. A Scepter supports that group; it is not the item that summons it.

Get a Tome of the Dark and learn its two actions

The Tome of the Dark summons a ranged bat. Wooden Crates, Winglings and Locked Copper Chests are among its loot sources. These are possible drops, not a guaranteed route from one specific chest.

With the tome selected, the Use action commands a minion. Secondary use summons one; hold the secondary action to summon or dismiss the group. Follow your platform's displayed binding, especially if you have remapped controls.

The update also removed the summon cooldown and added group summoning up to your current capacity. You no longer need to replace the group simply because an old lifespan timer ran out.

Add capacity without ignoring reserved mana

Active minions reserve mana, leaving less available for magic attacks. Check the amount you can actually cast with while the group is active. An extra slot is useful, but it is not a reason to ignore the rest of your loadout.

The Witch Doctor Hat is an early piece to look for. It adds 1 maximum minion and reduces minion mana reservation cost. Shroomans and Shrooman Brutes are among its random sources.

You can start using a tome before finding the hat. Treat it as an addition, not a mandatory drop that must appear before you are allowed to try summoning.

Use a Runestone Scepter to support the group

The Runestone Scepter applies a curse that makes minions deal 40% more damage to the cursed target. It is a magic weapon, so keep your tome for summoning and commanding.

Caveling Shamans, Malugaz the Corrupted and Locked Iron Chests are possible sources. None guarantees the Scepter on your next attempt.

Bring out your minions with the tome, then use the Scepter against the target you want them to damage. Keep another attack option available if your reserved mana leaves too little room for repeated casting.

This is a starter setup, not a best-in-slot list. Do not keep weak equipment solely for an extra summon if it leaves the rest of the character unsuitable for the next fight. Old lifespan-focused talent advice also needs checking: 1.3 replaced two summoning talents to fit persistent minions.