Neutral objective control and teamfight utility.
Durability and crowd control
Guard allies you cast spells on and those that are very nearby. If you or a guarded ally would take damage, you're both hasted and granted a shield.
Impairing the movement of an enemy champion marks them. Your allies heal when attacking champion's you've marked.
After 10 minutes gain 8 Armor and 8 Magic Resist and increase your total Armor and Magic Resist by 5%.
Heals and shields are 5% stronger and increased by an additional 10% on targets below 40% health.
+65 health and +10 AP or 6 AD, adaptive
Gain 3% extra MS. Gain extra AP or AD, based on your bonus MS, Adaptive.
Gain MS and AP or AD, Adaptive when in the river.
Guardian on Nunu allows you to massively empower a teammate in skirmishes and teamfights when you cast [W] on them.
The shield from Guardian scales well with Nunu's large health pool and the bonus haste with [W]s Movement Speed.
Font of Life allows you to provide considerable healing to teammates in teamfights where you're able to slow multiple targets at the same time with [E] and [R].
Conditioning allows you scale incredibly well into the mid game combined with Locket to make you a massive front-line tank.
Revitalize on Nunu empowers both the healing of your [Q] as well as the shielding of Guardian, Locket, and healing of Font of Life on teammates.
Celerity on Nunu provides a bit of Movement Speed for a faster jungle clear, as well as a bit of extra AP while [W] is on so you can chase down and finish off slowed targets.
Waterwalking on Nunu further enables you to control the river and take neutral objectives (Herald/Dragon )early and often.
Patch 8.10 saw a buff to Phase Rush and jungle duels for scuttle making Xin a powerhouse.