With all 24 IEM Rio Major teams now decided, their seeding order and matchups of the opening round of the Challengers Stage have been determined.

The Regional Major Ranking events concluded on Sunday following a week of action in Malta, Sweden, and Australia, and all 24 teams who will play at the first Brazilian Major taking place from October 31-November 13 are now known.

Specific seeding has been assigned to each team who has qualified for the Rio Major as per Valve's official Major rulebook and, as a result, the opening matchups of the first stage of the tournament have been set.

The rulebook outlines that teams are assigned their pre-event seeding based on the results of their region's representatives at the previous Major — the final ranking from the PGL Major Antwerp in this case.

For example, as the first-placed team from the Americas RMR, Liquid have inherited the Legends status and the overall eighth seed in the Legends Stage that FURIA earned for the region by making it to the quarter-finals in Antwerp five months ago. The other five Americas teams were assigned seeds 3, 8, 11, 12, and 15 in the Challengers Stage after their representatives were ranked 11th, 16th, 19th, 20th, and 23rd last time around in Belgium.

As a result of the aforementioned seeding method, the opening matchups of the IEM Rio Major Challengers Stage are the following:

Round 1
OG vs. Grayhound
Vitality vs. Imperial
Evil Geniuses vs. IHC
Cloud9 vs. fnatic
BIG vs. FURIA
Bad News Eagles vs. 00NATION
MOUZ vs. Outsiders
9z vs. GamerLegion

Below you can see the complete seeding order of each Swiss phase. This will be further used for round 2 of the Challengers Stage (right column) as well as for the first two rounds of the Legends Stage (left column).

It will also serve as a tiebreaking method when teams are tied in their difficulty score (the combined record of a team's previous opponents, also known as the Buchholz score), which is the primary seeding method for rounds 3-5.