Merlin's Fire-type Wizard Heart and Thunder-type Wizard Heart started to draw together slowly, and even fused gradually. Merlin could clearly tell that this was not an illusion! At least, with his current Mind Power, there was no Hallucinating spell which could trap him without him realizing it.
As for the Wizard Hearts in his body, Merlin sensed that they were incomparably real, only he was unable to control them. He could only watch powerlessly as the two Wizard Hearts slowly converged.
This was an undeniably true sensation. In his initial plan, he had decided to first fuse the Fire-type and Thunder-type Wizard Hearts as well. After all, his first spell fusion was between these two types.
The present situation was consistent with what Merlin had wanted.