From the very first moment she entered the Boss Room, Senna was completely aware of the danger faced to them by this Slime Prince. Panic starts to rise from within her chest, but in an instant, it halts and is replaced with calm, analytical observation. 

Think.

The boss was in the center of the room. On his hand, was one [i]"Acid Slime"[/i], red of colour and seemingly hiding itself on the hand of the Boss. There were no traps visible, and the entire floor consisted mostly of a large, circular stone plane, completely flat, and with solid stone walls. It was large enough for there to be some delay before the enemy's attack and it reaching them, hopefully.

See past the obvious.

The enemy called themselves a Metal Slime. The enemies they've been fighting up until now were Slimes. Weak point: Core. If its body consists of metal, then its core will be hard to reach, because they won't be able to see it from a distance. They'll have to fight it in close quarters eventually, so they'll be at a disadvantage in this fight, given the apparent invulnerability of Slimes besides their singular mortal point.

Then, the question was, could their weapons pierce the Metal Slime's body? It was worth using a few arrows to test this. And so, Senna reached her inevitable conclusion. Drawing a pair of arrows from her quiver, she locks her eyes onto the Slime Prince's body, visualizing her attack in her head, preforming thousands of minute adjustments to her draw strength, balance and firing arc. 

Hold breath. 
Count. 
Release.

An arrow is launched, in the direction of the slime prince, aimed directly at the being's chest. But, the girl wouldn't stop there. Her second arrow is drawn almost immediately, and once again, she takes careful aim at almost twice the speed of the previous shot, as her aim was already prepared beforehand. 

She didn't need to think. She fires again, aiming roughly at the torso of the Boss in front of her. 

Only then does she speak to her partner.

[i]"We need to feel it out first, to see if we can hurt it. Then we should probably back off, and try to find the others, so we can face it together."[/i]