What it does
Lord of the Pyrrhian Legions isn't actually a keyword—it's a creature card from the Mercadian Masques era. It's a 4/4 Soldier for 

with no abilities printed on it; it was famously included in sets as a vanilla-style legend, and its "ability" is essentially being a beater with no built-in protection or evasion.
The thing people get wrong is assuming it has a tribal "lord" effect (like pumping other Soldiers) because of its name. It doesn't—"Lord" here is just a title, not a rules term granting an anthem.
In Commander, it's largely a relic and rarely played competitively. If you do run it, treat it as raw stats only; build around it with equipment, evasion, or Soldier synergies from other cards, since the creature itself contributes nothing beyond a body and its legendary status.
