Summoning

"Is that true?"

"He will summon right now?"

"Wait, there's no Arcane Circle and Arcane Stone prepared. How can he start the Bestowal Ceremony?"

"Ahh… That's true…"

The practitioners were not doubting Ruthren's words but they are just confused about the process of summoning. 

The Arcana Bestowal Ceremony they know is when they hunted humans for their blood and sacrifice them to the Imp gods. 

During the process, a small void will appear at the place where they conducted the ritual to take the blood of the humans. 

After the gods took the blood they offered, they would have 10 seconds to state their wish.

If they wished for Arcana, they would normally receive a weapon or weapons depending on the quality and quantity of the blood they offered.