Trample Domain — Whenever Briar Hydra deals combat damage to a player, put X +1/+1 counters on target creature you control, where X is the number of basic land types among lands you control.
2022-09-09
Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.
2022-09-09
The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don't contribute to domain abilities.
2022-09-09
The value of X is determined as Briar Hydra's last ability resolves.