Noble Hierarch

If you declare exactly one creature as an attacker, each exalted ability on each permanent you control (including, perhaps, the attacking creature itself) will trigger.

In a Two-Headed Giant game, a creature “attacks alone” if it's the only creature declared as an attacker by your entire team. If you control that attacking creature, your exalted abilities will trigger but your teammate's exalted abilities won't.

You must attack with exactly one creature for exalted abilities to trigger. Exalted abilities won't trigger if you attack a player with one creature and a planeswalker with another, for example, or if you attack with two creatures but one is removed from combat.