Day 1

As you approach the doorway to the second alter Lucas spot 4 holes on the ceiling 5-10 feet past the doorway.

Meanwhile Bellow reach the room with second altar and see two more chest on the altar, but as he enter the room northern statue open one of ayes and amber light comes from the statue.

You all see Bellow running out of the room and the light shining through the doorway. Belliw stops at western wall. Light shines diagonally in west-south direction s he is out of the light but still terrified.
In a moment light goes out. But Bellow gets out of frightened condition only after a minute. Bellow roll arcana DC 15 to recall lore.

Bellow knows it was a magic that made him afraid, that was obvious. But he believe that the only way to cast magic when a creature say some magic words. So he believe that there is a creature in the statue who cast the spell at him. That would also explain why he didn't hear magic words.

Yes, you see (with a few second delay) the same amber light coming through doorway (but not reaching you as you stay away from it) . It stop shining in a moment just as previously. You see the stone shining one the floor inside the room.

Statues are almost 10 feet tall each.

Lucas, you don't see anything, but still have a feel that something dreadful is there in the statue, you could even feel that something inside of if (the feeling is irrational, just as usual for mind affecting magic).

Lucas: Perhaps closing ayes was a good idea, but you managed to withstand the dreadful feelings. Now as you open your ayes you only see a statue. Since you didn't see the moment when magic were cast you could roll arcana with disadvantage. DC 15.
Others You saw Lucas entering the room and the same light coming out of it, but Lucas stand still in the room breathing deeply.