
There have been multiple Arknights collaboration skins released in Delta Force during the last two seasons. If you’re looking to get the latest one, you need many Ark Force Cards, some of which you can get for free.
Here’s how to get Ark Force Cards in Delta Force and unlock Arknights collaboration skins.
How to get free Ark Force Cards in Delta Force

You can get free Ark Force Cards in Delta Force via the Ark Force Cards Giveaway event. It features a series of weekly challenges with simple objectives like logging in for a couple of days and playing any of the modes for a certain amount of time.
You can earn up to 90 free Ark Force Cards from the event, which is enough to do seven draws on any of the collaboration skin bundles. After using the free cards, you need to buy the rest with 100 Delta Tickets/Delta Coins per Ark Force Card.

During the Delta Force anniversary, there’s an Anniversary Giveaway Reloaded event that awards free Limited-Time Delta Tickets. These work the same as regular Delta Tickets, except they have an expiration date. You can use these to buy Ark Force Cards for the Arknights skins or anything else in the shop.
Arknights skin banners in Delta Force, explained

Arknights Force bundles with collaboration skins work the same as regular Research bundles. There are eight rewards in the loot pool, and there are no duplicate drops. Character skins are the grand prize, with only around a one percent chance to get at first, increasing as you get other rewards from the pool. Getting the grand prize early automatically grants all the other rewards in the pool.
Ark Force Card prices per draw increase incrementally: one, three, five, 10, 15, 20, 25, and 31. This means you need a total of 110 Ark Force Cards to guarantee all the rewards from the collection. If you’re buying them for cash, that’s around $135 worth of Delta Coins.