Any enters-the-battlefield abilities of the copied creature will trigger when Callidus Assassin enters the battlefield. You get to choose the order of those abilities and the triggered ability it has due to its copy effect. Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the chosen creature will also work.
If the chosen creature is copying something else (for example, if the chosen creature is another Callidus Assassin), then your Callidus Assassin enters the battlefield as whatever the chosen creature copied.
You can choose not to copy anything. In that case, Callidus Assassin enters the battlefield as a 3/3 creature. Notably, it does not have "When this creature enters the battlefield, destroy up to one other target creature with the same name as this creature."
Last observed on Scryfall 2 months ago at $15.94. Over the trailing 90 days the price moved between $15.94 and $19.06 across 52 observations. Cross-checked across TCGplayer, eBay sold, Cardmarket EU, and Star City.
This printing is one of 2 catalogued treatments from 40K — the lineup includes Foil alongside the standard finish. Across our catalog the Rarix library tracks every variant in the same family so collectors can compare price, scarcity and demand inside a single lineage.
Card #109★ of *Warhammer 40,000 Commander*, the set that shipped alongside the October 2022 Warhammer 40,000 Commander release.
Card type: Creature — Human Shapeshifter Assassin, color identity black/blue, printed at rare. Rares occupy the bottom-of-pack rare slot in standard boosters. Mana cost: {4}{U}{B} (6 converted). Keyword abilities: Polymorphine and Flash.
Legal in Legacy, Vintage, and Commander.
EDHrec ranks this card #5,410 in Commander, putting it in the niche-pick tier of the format's playable pool.
Illustrated by Bryan Sola. Rarix catalogs 261 other cards credited to this artist.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Bryan Sola
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
The triggered ability that Callidus Assassin has is part of its copy effect and is a copiable value that other effects may copy.
Callidus Assassin copies exactly what was printed on the original creature (unless that creature is copying something else or is a token; see below) and it has the triggered ability. It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or any Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.
If the chosen creature is a token, Callidus Assassin copies the original characteristics of that token as stated by the effect that created the token. Callidus Assassin is not a token in this case.
If Callidus Assassin somehow enters the battlefield at the same time as another creature, Callidus Assassin can't become a copy of that creature. You may choose only a creature that's already on the battlefield.
