When you summon a creature, the summoned creature’s level cannot exceed the level of the creature summoning it, unless the summoning effect explicitly says otherwise.
Each player has a Summon Cap: the maximum number of summoned creatures they can control at the same time.
If you would gain control of summons beyond your Summon Cap, you must immediately choose which summons you keep.
Any summons not kept immediately end (they disappear), unless a rule specifically says they persist.
A summoned creature follows all of the rules below unless an effect says otherwise:
Actions
A summoned creature has 2 actions.
A summoned creature has no reaction (so it cannot use reaction-based abilities, including Ready if your system treats Ready as a reaction).
Duration / Maintenance
A summoned creature disappears if you are no longer maintaining the effect that summoned it (for example, if you stop Concentrating or you stop Sustaining, depending on the effect).