Doing It for Kathril (EDH / Commander)

This deck is a modified build of the 2020 commander precon "Symbiotic Swarm".

The main strategy is to dump creatures that have printed keywords into your graveyard to allow Kathril, Aspect Warper's ETB effect to generate as many counters as possible, then swing hard to knock out other players with commander damage.

An alternate play is to go wide with Eerie Ultimatum and resurrect as many dumped creatures as possible. This is best used when you can resurrect Akroma, Vision of Ixidor alongside other keyword creatures.

Dumping creatures is done mainly via self-mill cards such as Grisly Salvage, Perpetual Timepiece, and Nyx Weaver. There are also cards that put creatures directly from the library into the graveyard such as Buried Alive and Gravebreaker Lamia.

The highest number of individual keywords you can get into the graveyard by using Buried Alive is nine. This is done by sending Bassara Tower Archer, Leyline Prowler, and Zetalpa, Primal Dawn.

This build also makes good use of flicker cards such as Cloudshift and Ephemerate since Kathril's counter generation is an ETB effect and says you can put the keyword counters "on any creature you control". Combine this with The Ozolith to also hold on to the +1/+1 counters Kathril would lose when it flickers.

Since this deck's strategy is easily disrupted by graveyard hate, it's important to try not to put more keyword creatures than you need into your graveyard all at once. If you have a decent amount, start holding on to your library-to-graveyard spells in case your opponents target you with Bojuka Bog or Soul-Guide Lantern. A good rule of thumb to follow when editing the deck is to have at the very least least two appearances of each relevant keyword.

It's also important to mentally keep stock of what keyword creatures are still left in your deck. For example, if you're planning to use Entomb to put a creature with double strike into your graveyard, and Bontu the Glorified is already there, you might consider choosing something other than Oketra the True since indestructible is valuable keyword that you won't want to be doubled-up on if your graveyard gets exiled.