In this rule

Historical Rules · 5 October 2018

Rule 701.36c

Official source text from the 5 October 2018 Rules release

Permalink

If an effect instructs a player to meld cards that can’t be melded, they stay in their current zone. Example: A player owns and controls Midnight Scavengers and a token that’s a copy of Graf Rats. At the beginning of combat, both are exiled but can’t be melded. Midnight Scavengers remains exiled and the exiled token ceases to exist.

Find this number in the current Rules