Celtic Frost's frontman, guitarist and singer Tom Gabriel Fischer, adopted the alias Tom Warrior. With Steve Warrior on bass, he formed one of the earliest extreme metal bands, Hellhammer, in 1981. Steve Warrior was later replaced by Martin Eric Ain - also a pseudonym. The band attracted a small international fan-base, got signed to Noise Records in Germany and recorded their debut EP Apocalyptic Raids in March 1984, now a rare find on eBay or second-hand record stores around the world.  Metal publications were also skeptical of Hellhammer's musical endeavor. Metal Forces loathed the group; that started a long-lasting feud between that zine and Warrior, which kept Celtic Frost from playing in England for a couple of years. Rock Power was not fond of Hellhammer either - they considered it "the most terrible, abhorrent, and atrocious thing 'musicians' were ever allowed to record". In fact, they were "receiving miserable reviews everywhere", Warrior concluded.  Regarding the controversial status of his former band, Thomas said:  Way back in 1984 and 85, when Martin Eric Ain and I recorded Celtic Frost's first two albums Morbid Tales and To Mega Therion, Hellhammer lasted on us almost like a curse. Even though Hellhammer was the very reason we had thought over our goals and conceived the Frost, HH's left-overs kept being mighty rocks in our way. Many voices saw Frost as the same band with just a name-change. The lack of musical quality in HH made it almost impossible for us to get an unbiased reaction for Frost. To make a long story short, it almost killed all our work and dreams.  By May 1984, Hellhammer had disbanded. Fischer and Ain, along with session drummer Stephen Priestly, regrouped as Celtic Frost. Their 1984 debut mini-LP, Morbid Tales was a hit in the underground metal scene, and the band set out on its first tour, through Germany and Austria. This was followed with an EP Emperor's Return. Both early releases are now available on the one CD.

Answer this question "Who else was part of this band?" by extracting the answer from the text above.
Steve Warrior