Casualty 2 means "As an additional cost to cast this spell, you may sacrifice a creature with power 2 or greater." and "When you cast this spell, if a casualty cost was paid for it, copy it
But then the rules text and the gameplay it endorses sink in and you realize this: by simply having it on the battlefield, the game is bound to end with as little as an additional blue mana in the most dramatic of ways
All in all, Helm of the Ghastlord is a pretty fun card for lower-bracket Voltron Commander strategies - decks that want to win the game by making their commander huge so they can deal 21 points of commander damage as quickly as possible
Lead with Gisa and Geralf ($0.37) and lean on cards that cost less than a coffee: Lords: Diregraf Captain ($0.44), Cemetery Reaper ($0.46), Undead Warchief, Lord of the Accursed
Anytime anyone sacrifices any creatures for any reason, Thraximundar gets +1/+1