Some commanders are considered to be "glass cannons", in the sense that all the offensive power of the deck is concentrated through a single creature. If that creature is repeatedly removed or otherwise subdued, then the deck just stops being a threat. However, if that creature has enough protection or can evade detrimental spells, then your opponents get to witness the power of the fully operational battle station that is your deck. Mairsil, the Pretender is one of these commanders.

Upon entering the battlefield, Mairsil can "cage" another artifact or creature in your hand or graveyard and then Mairsil himself gains all of that card's activated abilities. As Mairsil puts more cards in the cage and expands his prison menagerie, he gains more abilities. Actually casting any of those cards is often a last resort, but since he can cage things in your graveyard, it's not terrible to throw them out on the field as expendables and then cage them later after they are dead.

Search Filters

There are quite a lot of artifacts and creatures with activated abilities, so this article will be heavy on the card search filters. We'll also explore how to format our queries specifically for the scryfall.com search engine. For starters, let's look for artifacts or creatures with Type: OR creature OR artifact. Then filter out the colors we aren't using with Color: NOT green NOT white. Depending upon your search engine, this might be possible by searching within a Grixis color identity instead of filtering out green and white from the mana costs.

Luckily for us, every card with an activated ability has a colon punctuation mark in the rules text. Text: AND ":"

A few cards have activated abilities that require paying mana outside of the card's colors, so let's filter out cards that have those mana symbols in the text with Text: NOT {G} NOT {W}. If our search engine uses color identity instead of just mana cost, then this step may not be needed.

As an example, here's an applicable search string that can be used on Scryfall for the above stipulations.

Scryfall: (t:creature or t:artifact) id<=rbu o:":"

Including everything up through the Ixilan set, that returns only 2,440 results. No problem...

Let's narrow that down further by excluding certain activated abilities that specifically do not work well when Mairsil tries to do them. Mairsil has to be on the field to have the abilities, so abilities that rely upon being in your hand or graveyard are not very useful. Also, Mairsil is not an Equipment, Vehicle, or sliver, so some more terms can be excluded. Text: NOT cycling NOT unearth NOT embalm NOT ninjutsu NOT equip NOT crew NOT "all slivers". Only 2,370 results. Not much of a reduction, but I'll take it.

Theme

After all those filters, the number of card choices remaining can still be overwhelming. This also means that there is plenty of variety available to build whatever type of Mairsil deck you want.

At the time of writing, this past Friday fell on the 13th of October. We are now moving into the second half of October, which means it's Halloween season. As a thematic choice for this article, I'll show you how to build Mairsil as if he were Jason Vorhees, the indestructible solitary serial killer who hacked and chopped his way through the course of eleven fine cinematic masterpieces known collectively as the "Friday the 13th series".

This particular deck will use Mairsil in combat, so we want to avoid using too many cards that require tapping to activate an ability, since that interferes with Mairsil tapping to attack. The tap symbol is often represented in databases as {T}. Text: NOT "{T}". 1,210 results. Yay!

Scryfall: (t:creature or t:artifact) id<=rbu o:":" -o:cycling -o:unearth -o:embalm -o:ninjutsu -o:equip -o:crew -o:"all slivers" -o:"{T}"

(Yes, I know tapping Mairsil as a Tree of Perdition is effective, as I said in my podcast on the subject. We're trying something different here.)

Mana-Free Regeneration

Based on his behavior in the films, we know that Jason Vorhees can regenerate. Suppose we want to find cards that do not cost mana to activate an ability to regenerate. In that case, we filter out the mana symbols that we don't want to see from the card rules text. Most search engines use {curly brackets} around a mana color, like {R} {U} {B} for red blue black or {1} {2} {3} for generic mana of those amounts. You may also occasionally see snow-covered mana which is often represented by {S}. Suppose we also want abilities that do not require sacrificing something. In total, this filter adds up to quite a mouthful...

Scryfall: (t:creature or t:artifact) id<=rbu o:":" -o:cycling -o:unearth -o:embalm -o:ninjutsu -o:equip -o:crew -o:"all slivers" -o:"{T}" -o:{B} -o:{R} -o:{U} -o:{1} -o:{2} -o:{3} -o:{4} -o:{S} -o:sacrifice o:regenerate

Only eight results. That's more like it! Most of these are playable. Grotesque Hybrid snuck through because it says "can't be regenerated", but it works well in this deck for its combat enchancement.

Discard as a Cost

As a reminder, Mairsil can cage things that are in your graveyard. Discarding a card as part of the cost for an ability is not a real drawback, except when opponents are using graveyard exile effects. In most cases, the worst that happens is that your opponents get to experience the foreboding tension of seeing the next terrible nightmare that you will inevitably add to your repertoire. This matches the theme of horror films quite well. Let's browse these cards and see what is there. I've edited out some cards from the following list that aren't particularly useful to Mairsil's situation.

Scryfall: (t:creature or t:artifact) id<=rbu o:":" -o:cycling -o:unearth -o:embalm -o:ninjutsu -o:equip -o:crew -o:"all slivers" -o:"{T}" -o:{B} -o:{R} -o:{U} -o:{1} -o:{2} -o:{3} -o:{4} -o:{S} -o:sacrifice o:discard

Untap as a Cost

In addition to regeneration, we know that every time Jason Vorhees gets knocked down he just gets right back up again. Let's simulate that by finding ways to untap Mairsil. Some abilities require untapping as part of the ability cost. This is often signified by search engines as {Q}, for some reason.

Scryfall: (t:creature or t:artifact) id<=rbu o:":" o:{Q}

The Deck

Remember that this is a theme deck based on Jason Vorhees. In the fashion of the horror series, he's a solitary guy without any allies. Thus, in a very non-Grixis fashion, this deck does not try to take control of opponent creature cards. Of course, other Mairsil decks could do this easily in a variety of ways, such as Captivating Crew, Memnarch, or Olivia Voldaren for the living, or The Scarab God, Geth, Lord of the Vault, or Havengul Lich for the dead. But this deck isn't doing that. He also isn't going to have accomplices helping him on the field, like Deadeye Navigator or Sakashima the Impostor. *Spoiler* That might be fine for the Scream films, but not this series.

This is a voltron deck where Mairsil Vorhees wins by attacking all by himself. Deathtouch fits the theme. Unblockable is good, but shadow is thematically better. Infect is fair game. As an extra brewing challenge, none of the creatures' activated abilities in this deck require Mairsil to tap. Note that the creature section is not sorted by mana cost, because if the deck is played correctly to theme, none of those creatures will ever be cast and thus their mana costs are irrelevant.

Enjoy...