The usual. You are a Master performing the typical invocation of Servants... the Summoning Circle rotates and an unusual figure manifests... Uh?

"No world or barrier can hold me! I have finally come to the famous Chaldea! The lovely butterfly of the moon...BB, the Moon Cancer, has been summoned! Well, this is just a temporary arrangement, but take good care of me, little Master!" Being in a pose with hands on hips and a confident smile.

Why doesn't that smile give you so much confidence?