Persistent Summon Monster (3.5e Spell)

You keep cutting down dretch after dretch, but the buggers keep coming!

You quickly draw a 5 foot wide eldritch summoning circle made of light on the ground or nearby wall and summon creatures from it as if using a summon monster spell two levels lower. In exchanged for the weaker power, you gain the ability to have your summons respawn automatically for the duration. When all your summons have been destroyed, they will respawn 1 round after the last summon dies at the summoning circle, as if you had cast the same summon monster spell again.They will continue to respawn and fight for you until the duration is up or the summoning circle is destroyed. The summoning circle is subject to dispel attempts, or if the surface the summoning circle is drawn on is destroyed. You can destroy all your current summons as a standard action to force them to respawn.

You can place this spell in a higher level spell slot, thus gaining stronger and stronger summoned monsters. For example at 9th level spell slots, this can continously summon summon monster VII creatures.

This spell otherwise acts and counts as summon monster.

Arcane Focus:  A tiny bag and a small (not necessarily lit) candle.