Astartes Project by Syama Pedersen

Parts 1 - 5 of the Astartes Project by Syama Pedersen

Much better that some of the official animations made through GamesWorkShop

Even if you know nothing of WH40k its pretty epic animation:

Space Marines are sent to recover a relic of sort, only to find some sort of psyker cyber hosts guarding it, being space marines they push through, but it being WH40k, theres never a happy ending.