Can Sett leader protect a unit at your base from a spell that would kill it?

Ruling: Yes, Sett leader can protect a unit already at your base from being killed. The targeting requirement is just a buffed unit you control, with no restriction on location.

Sequence:

• Pay the cost including the buff requirement
• Exhaust Sett leader and recycle a rune
• The unit doesn't die
• The recall portion is ignored under the "do as much as possible" rule since the unit is already at the base

Nuances:

• You must still pay the full cost including placing a buff on the unit, even though it's already at the base
• The recall effect simply doesn't do anything when the unit is already at the base, but the protection still applies