I got a Knight servant from a Deck of Many Things, and am looking at his Leadership ability.
For 1 minute, the knight can utter a special command or warning whenever a nonhostile creature that it can see within 30 ft. of it makes an attack roll or a saving throw. The creature can add a d4 to its roll provided it can hear and understand the knight. A creature can benefit from only one Leadership die at a time. This effect ends if the knight is incapacitated.
The highlighted sentence seems to me that it focuses on having multiple Knights, and their Leadership not stacking. If you make 2 attacks, you can have 1 dice on the first attack, and another on the second, and you don't have 2 dice at a time.
I'm playing a Bard, with my very limited Inspiration dice, and feel his ability is really strong. Since there is no apparent cost, can the Knight essentially give an extra 1d4 to all attack rolls and saving throws of my party (including himself) for 1 minute?
I know 1d4 isn't much, but multiplied by 10 rolls per round (a few extra attacks and a couple of saves by 5 party members) for 10 rounds really adds up!