A neat sideboard piece that takes on a few decks that haven't had much in the way of direct hate pieces, Stifle Progress shuts down both counter decks, mainly Angels, Ethelhime, and Duxvox, while the anti-reveal effect line stops mainly Ethelhime Alehouse, as well as Swift, some Demon hand-hate pieces, and various other reveal cards.

The main place where this is likely to be an effective sideboard piece is against Ethelhime, where the first ability shuts down the Alehouse Counter generation, and therefore can shut down Ethelhime's main win-conditions. The in-discard effect also shuts down Ethel, letting you threaten to shut down the Alehouse for 2 turns in a row.

The counter prevention largely acts as a proactive variant of the more reactive Land Of Defiance. Whilst this one is far more telegraphed, it can potentially shut down any Angel deck for an entire turn.

The anti-reveal again will be most relevant against Ethelhime, but potentially has use against decks like Sapphire Storm, albeit only in decks able to get the card into the discard pile.

Our third Warlock, Ariyus once again brings a powerful Swift ability to break up an opponent's turn, this time interrupting the burn effect damage out of decks like Black Magic, and Lost Messiah. This could potentially be relevant against Burn Orcs too, but to a smaller degree.

Importantly, there aren't a ton of ways to beat out Ariyus in response to a huge burn effect like Castiel's Oblation or Ermadexa's Scour. Since Ariyus doesn't have any Keyword abilities that will trigger on play, you won't have a window of opportunity to remove Ariyus on the sequence before your win-condition is absorbed by Soulbind. Majik Void Collapse is one way to stop Soulbind, but for both Castiel and Adramelech, Void Collapse is a card that hurts a crucial portion of your deck. As such, it'll be a predicament on whether it's worth the inclusion of Void Collapse in the sideboard to stop Ariyus.

Ariyus will be competing with Alburdunn's Mayoral Announcement for sideboard slots, but both cards fill a relevant use case. Ariyus, The Soulbound Warlock has the advantage of being significantly more difficult to play around, letting you ambush Castiel or Adramelech players. In contrast, Mayoral Announcement is heavily telegraphed by nature of being a Unified, but has it's own synergy with a Viviana sideboard package and is better into incremental effect damage decks such as Mal'ady or Gaia.

Ultimately, both of these Warlords will remain reasonably powerful threats in the metagame, but Ariyus certainly presents a hate-piece more resilient against copies of Freelia and unified negate pieces.