Sephiroth was in control.

>>320252335
Jenova was pretty much in the background all the time , Sephiroth was messing shit up on his own

>>320252335
It was a partnership

The original Sephiroth stopped existing once he came into contact with Jenova at the reactor.

That new Sephiroth acted of his violition but he basically inherited Jenova's will after first contact.

Jenova is an analogy for judaism.

>>320252335
>Sephiroth controls Jenova

Nigga please he thought Jenova was his Mother he wouldn't control her

>>320252335
In the game it's kinda ambiguous. Sephiroth appears to be in control, and believes he's carrying out Jenova's will as his destiny, but that's the basic intention of all Jenova lifeforms, presumably. He's a fusion of humanity and Jenova; he believes he has free choice to carry out the will of Jenova, but he also effectively IS Jenova in part, so it could just be the basic instinct of his Jenova cells kicking in.

Then again, AC has 3 characters that are literal physical manifestations of Sephiroth's will, so that adds another layer to things.

>>320252335
Ignoring the katana edgelord aspect, this guy was a pretty good tragic villain. Shame his reputation got tarnished so much.

The game does not answer the question who the entity in Northern Crater is.

Thematically, it would be more appropriate for it to be Jenova that has taken the form of Sephiroth, since Sephiroth seemingly 'haunts' the player and Cloud in a very ghost-like manner (taking the form of other people, flying, phasing through walls, possessing Cloud). This very much implies that Sephiroth is dead and the goal is to EXORCISE him, Cloud already defeated him in Nibelheim and it's therefore safe to assume Sephiroth really did die back then. Jenova is using the memory of Sephiroth as a weapon.

I think Sephiroth doesn't have a physical form anymore but controls Jenova from the Lifestream to do all the work