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Back to the terrain question: a promotion zone does not constitute terrain for me, also the forward direction of pawns is not dictated by terrain.

Holes in the the board are somewhat strange to Chess and may constitute terrain. Barriers of all kind are certainly terrain.

Possible terrain effect are: Difficult terrain (mountains, swamps) slowing units (pieces) down or forbidding some kind of pieces (two heavy to move there ...) on that terrain, land/water distinction (land units need boats or bridges to cross the water, water units cannot move on land (but maybe shoot units down on land), air planes can operate both on land and water, but need to land after some time and need airports or carriers for this purpose), cities (providing supplies fo any kind, generating new units, allowing of repair of damaged units).

This leads to another chess criterion

[24] A chess piece is either fully functional or captured, there is no such thing like 'damage' or 'health' with consequences to the piece (slower motion, need of repair, easier capturability). Of course, a bad position (e.g. pinned) does not count as damage. In FIDE chess the only (very mild) violation of the no damage rule is the loss of castling rights.