You need to be a subscriber of Amazon Prime and be a Twitch Prime member (free with the Amazon Prime subscription) to claim the loot. Once you claim it though it will also be available on any platform.
What's more is that you don't have to choose a platform to lock it down to. It'll be available on any platform you have DOOM Eternal on. So if you own the game on Stadia and on PC or console, you can use it on all of those platforms.
The DOOM Eternal Mullet Slayer skin comes with extras
Technically the Mullet Slayer is three different skins. Because you get three variations of it. You have the Mullet Slayer, then there's two additional skin variants called American Made, and Business In The Front.
All of them are still technically the Mullet Slayer, but with different undersized t-shirts. As serious and chaotic as DOOM Eternal can be with all the demon killing, a little satire here and there is a welcomed addition to the game.
From the mullet and stache down to the six pack of beers on each wrist, this is one skin you will definitely want to play with. Especially for the cinematics because it will show up in them.
Aside from the slayer skins, you also get a handful of different customizations. Including a new stance, a new victory animation, and a couple of new podium skins called Home Sweet Home and The Den.
Everything really comes together when you toss on the Mullet Slayer skin and the Home Sweet Home Podium, then play the "Yup" stance. You can view that in the tweet below.
This is the second loot drop, and there still two more to go
Many of the Twitch Prime drops include multiple months of loot. The Destiny 2 loot drops for example are set to continue for a few months, totaling six since the first one was released.
DOOM Eternal just had its second drop with this latest one, and there are two more before the end. You have the Doomicorn drop which landed at launch with the game. Then this one with the Mullet Slayer.
There will be another drop following in June and one in July. So far though, no exact dates have been set for when those release, and there's no telling what the content is. Either way you still have plenty of time to become a Twitch Prime member before you lose out on these awesome skins for the character.
— JD (@JDNews4) May 21, 2020