Another reason for your suggestion of Nature or Trickery Domain is how very well it ties into Firbolg lore. As creatures with fey ancestry, It will be only fitting to get a character to have a adore on the natural world or to have a little mischief in them.

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When the goliath avenger makes an Athletics Test to jump or climb, roll 2 times and use both result.

When the goliath ranger makes an Athletics check to jump or climb, roll 2 times and use possibly outcome.

When the goliath fighter makes an Athletics Examine to leap

I'm guessing the "Orc" playable race from Volo's Guide will likely be pretty great also, but I haven't seriously taken a look at that nevertheless, so I don't know without a rulebook before me.

Artificer: Artificers need INT being productive. Updated: With