Matthew Walker, also known as Ari, is a professional Dota 2 player from the United Kingdom. His signature heroes are Rubick, Snapfire, and Pugna.

Ari started his esports career in 2022 when he joined the British multigaming club, Into the Breach. His first tournament was the online event Dota 2 Champions League Season 7, where he placed 16-17th. Throughout the DPC WEU 2021/2022 Tour 3: Division II and 1x Series season, Into the Breach placed second on the tournament leaderboard and also competed in Last-Last Chance and European Pro League Season 4, where they secured third place. Additionally, he and the team participated in the qualifiers for The International 2022.

Later in 2022, Ari left Into the Breach and joined TSM as a support player, joining teammates from Indonesia, Russia, the UK, Peru, and Canada. The team quickly competed in DPC NA 2023 Tour 1: Division I, where they finished first and earned $6,000. They also participated in The Lima Major 2023, where they finished in the 13-14th place.

In the 2023/2024 season, Ari moved to OG but failed to qualify for ESL One: Kuala Lumpur 2023. In 2024, Ari continued to play for OG and won prizes at DreamLeague Season 22, BetBoom Dacha Dubai 2024, ESL One: Birmingham 2024, Elite League 2024, FISSURE Universe Ep.2 and Riyadh Masters 2024.

In September, OG introduced a new roster that included 23Savage, returning from inactivity Nine, Wisper, Ari, and Seb. With this lineup, the team participated in the qualifiers for the BetBoom Dacha Belgrade 2024. Later, the team failed a few more qualifications for major tournaments, and after competing at the 1win Series Dota 2 Fall, finishing in 7th place. The team also performed poorly at BLAST SLAM I, finishing in 9th-10th place.

On January 29, 2025, OG moved Ari to the inactive roster.

In March 2025, Ari joined the Natus Vincere organization on loan.

On April 11 of the same year, as part of Natus Vincere, they confidently defeated Rabotyagi in the grand final of CCT Dota 2 Series 8, winning 3:0 and becoming the tournament champions.

In June 2025, it became known that starting from July 1, Natus Vincere’s main roster will be disbanded and Ari was put on the transfer list.

On June 28, 2025, Natus Vincere participated in PGL Wallachia Season 5. The team lost in the lower bracket quarterfinals and finished the tournament in 5th–6th place.

June 29, 2025, just before the match against BetBoom Team at PGL Wallachia Season 5, Team Liquid made a substitution due to the deteriorating health of Aydin Insania Sarkohi, Ari stepped in for him, Team Liquid couldn’t defeat BetBoom Team with a stand-in, and thus the team leaves the tournament in 3rd place.

• September 29, 2025 — Ari joined Tundra Esports.

At the end of October, Tundra participated in FISSURE PLAYGROUND 2, where they finished in 6th–8th place after losing in the first round of the Playoff stage. At the following tournament, PGL Wallachia Season 6, the team finished in 7–8th place.

At the beginning of December, Tundra competed at BLAST Slam V, where they became champions. In the grand final, the team failed to overcome Team Yandex, losing 3-0. It is worth noting that Tundra has participated in every final of the BLAST series, and this victory marked their fourth consecutive championship. At DreamLeague Season 27, the team finished in fifth place, and at BLAST SLAM VI, the team didn't even make it to the playoffs.

At the end of March, Tundra became the champion of ESL One Birmingham 2026, defeating Team Yandex with a 3:1 score in the grand final.

The next tournament for the team was PGL Wallachia Season 8, where they played with stand-in. The team finished in 15-16 place, marking one of their worst results.