1990
He made his debut at the 1990 Survivor Series as the mystery partner for Ted DiBiase's "Million Dollar Team" (Undertaker, Ted DiBiase, and Rhythm & Blues). There opponents that night were the "Dream Team" (Dusty Rhodes, Bret Hart, Jim Neidhart, and Koko B. Ware). The Undertaker went on to pin both Koko B. Ware and Dusty Rhodes before getting counted out while he wasn't even the legal man!
1991
The Undertaker made his next big impact at Wrestlemania VII when he disposed of "Superfly" Jimmy Snuka. Snuka would not be seen in the WWF again until 1996.
The biggest impact he had betweem Wrestlemania VII and Survivor Series '91 was after the Macho Man and Elizabeth wedding at Summerslam '91, The Undertaker and Jake "The Snake" Roberts crashed the reception.
At Survivor Series '91 The Undertaker got his first title shot against Hulk Hogan. The Undertaker came into this match still without his first defeat. The match saw Hulk Hogan giving shot after shot to the Undertaker yet not being able to bring him down. The Undertaker tombstoned the "Hulkster" but Hulk Hogan kicked out. Hogan was finally able to knock the Undertaker down, but Ric Flair made his way to ringside. While Hogan was distracted by Flair, the Undertaker got up and was able to tombstone Hogan on a chair that Flair slid into the ring. The Undertaker got the pin and the title. After the match Hogan was out for about 3 minutes before being helped back to the locker room.
A rematch was scheduled the next week which Hogan won when hitting the Undertaker in the head with the urn, thus ending the Undertaker's first title reign.
1992-1993
1994-1995
1996-1997

1992At the 1992 Royal Rumble the Undertaker was looking to clean house. He preceeded to eliminate a few guys before "the Hulkster" came down to the ring. Within his first minute in the ring, Hogan eliminated the Undertaker.At Wrestlemania VIII the Undertaker was put against Jake "The Snake" Roberts. Roberts didn't pose much of a challenge as the Undertaker pinned him in about 7 minutes.When Summerslam '92 came around the Undertaker was being challenged by Kamala. Kamala seemed to be terrified by the Undertaker and the casket brought to ringside. The Undertaker dominated Kamala. Kamala attempted intemidate the Undertaker but failed horribly. The Undertaker continued the dominance until Kamala fled with the Undertaker stalking him.The two met in a rematch at Survivor Series '92 in a Coffin Match. This match would lead the way to what would later be know as a casket match. In this match, however, the rules were to pin your opponent, put him in the coffin, and nail the lid shut. Kamala, obviously terrified of the Undertaker, proved to be not much of a match for the Undertaker. The Undertaker pinned Kamala and threw him into the casket.1993At the '93 Royal Rumble the Undertaker was involved in the Royal Rumble match. He came to the ring taking care of several guys before Giant Gonzales, who wasn't entered in the Royal Rumble, made his way to ringside. Being led by Harry Wendlesteit, the former manager of Kamala, Giant Gonzales seemed to be focus on the Undertaker. The Undertaker took the worst beating he had ever taken since coming into the WWF.Giant Gonzales was the Undertaker's opponent at Wreslemania IX. After 7 minutes of a basically even match, Giant Gonzales put a rag over the mouth of the Undertaker, knocking him out. Gonzales was disqualified and the Undertaker was brought out of the ring on a stretcher. A moment later, a bell tolled in the arena. The Undertaker made his way back to the ring. Giant Gonzales and Harry Wendlesteit fled. The Undertaker would seek revenge.Before Summerslam, Paul Bearer came up missing. He was even rumored to be dead. Wendlesteit had possession of the Undertaker's urn. Giant Gonzales was again the Undertaker's opponent at Summerslam '93. The match was a "Rest In Peace" match. I'm not sure what the difference was than a regular match, but I believe it was no disqualifications. The match went back and forth for a while. About 6 minutes into the match the Undertaker went after the urn only to have Wendlesteit snatch it away at the last moment. The Undertaker dove between the Giant Gonzales' legs reaching out for the urn once more when bells went off in the arena. Down the entrance way came Paul Bearer carring a black wreath. Harry Wendlesteit immediately came after Paul Bearer only to be knocked down by a Bearer forearm. With Wendlesteit out of the way, Paul went for the urn and recovered it. A short time later the Undertaker connected with a flying closeline from the top rope on Giant Gonzales for the pin. After the match, Giant Gonzales chokeslamed Harry Wendlesteit in frustration from the defeat.At Survivor Series '93, the "All Americans" (Lex Luger, The Steiner Brothers, and Tatanka) were scheduled to face the "Foreign Fanatics" (Yokozuna, Crush, Ludwig)in a Survivor Series rules match. However, a few weeks before Survivor Series, Tatanka was hurt in a match on Raw, therefore being knocked out of competition for Survivor Series. His replacement was none other than the Undertaker. In the match, the Undertaker didn't enter the match 'til about half-way into it. When entering, he took on Yokozuna. The Undertaker put up a great fight but was eventually knocked down. Yokozuna pulled the Undertaker over to the turnbuckle and executed a Banzai Drop. However, the Undertaker sat up. Seeing this, Yokozuna was in shock. No one had ever kicked out of a Banzai Drop. The Undertaker went after Yokozuna, eventually fighting their way to the ringside area. Both Yokozuna and the Undertaker were counted out, but continued to fight there way to the back. Moments later Lex Luger made the final pin giving the All Americans the victory.1990-19911994-19951996-1997