His Comprehend ran out a while ago and now he needs to convey desperate urgency through the sole channel of 'I picked up a magic dagger because I was afraid' Merry the halfling. He'd hoped they might have seen something of the fight below, but apparently they sensibly hid out of sight while he charged a bunch of wraiths like a madman. Well, at least they're not celebrating a fake victory.
"The wraiths are stronger than I expected. By the time I got there there were only four, I don't know where the other two went - where are the other two halflings? - you should get them to come back here."
"I hurt them with magic but not enough to destroy any of them; I'm not sure if I could destroy one, definitely not tonight. Any weapon that hit them shriveled up after one strike, even my magic sword, look" - he gets the sad remains out of his bag. (They are still far too large to fit in the bag, and his hand went suspiciously deep inside it before he pulled it out.) "They also have magic daggers they can parry and hit back with, one of them got me and it's definitely drained me some, so they're very dangerous even in daylight. They got away, one's still got its horse, another horse is dead and the last one's wounded. And they can be completely invisible if they remove their cloaks."
"Which is to say that if any of them find any of us during the night, and they want us dead, we'll be dead. I don't know what game they were playing with you before now but I'm not going to rely on it continuing."