Skyrim Secondaries Intersection- Saarthal: Confluence Conclusion

Bizarre magickal effects aside, fighting Jyrik is thankfully simple once his defenses come down, so if you can prevent him dealing too much damage to you at the outset of the fight you'll be in a very good position.

On slaying the undead, Tolfdir rejoins you, exclaiming over the extraordinariness of the room and its contents (and continuing to do so until you speak to him).  Jyrik carries a few elements of gear, his portion of the Gauldur Amulet ( which provides a 30-point increase to Magicka pool when worn) and his Writ of Sealing.  These are needed for the Forbidden Legend sequence of quests.  On the table in front of Jyrik's throne is his staff, which blasts enemies with electricity, doing noteable damage to their Health and twice as much to their Magicka.

When you finally speak to Tolfdir, you can ask him about the stone sphere- he will ramble on about how amazing it is for a bit and then inform you that the Arch-Mage needs to be told about what's happened here and what the two of you have found.  He is not, however, willing to leave the thing unattended (for good reason- who needs random graverobbers suddenly becoming indestructible?) and wishes for you to return on your own.  This quest leads you to continue your string of tasks for the College of Winterhold.

Head around the floating orb and through the door behind it to find a hallway leading to your other rewards within the dungeon- a Word Wall containing one of the three pieces of the Ice Form Thu'um, and a chest that likely holds a couple of interesting bits of gear.

To the left of the Word Wall is a door which brings you out in the upper layers of the Saarthal Excavation, where use of a handle on the wall lets you out of a porticullis just over a wooden ramp.  Use this to depart and get back to- well, whatever it was you were doing out there.