Durak
Transfer Durak: the variant that sends the attack round the table
In the transfer variant a defender can pass the whole attack on with one card. It sounds small. It changes almost every decision.
Most people who learned Durak at home played the throw-in version, podkidnoy. The other common version is transfer Durak, perevodnoy, and players who grew up with one often find the other strange.
The rule
Before beating anything, the defender may add a card of the same rank as the attack and pass the whole attack to the next player on their left. That player now defends against a bigger attack, and may transfer it again if they hold the rank too. Transfers can chain round the table.
Two limits apply. The next player must have enough cards to face the attack. And once any card in the bout has been beaten, transferring is no longer allowed.
A common house rule lets a defender transfer by showing a trump of the right rank instead of playing it, keeping the trump in hand.
What changes
Pairs become much stronger. With two cards of one rank you can attack, and if the attack comes back round to you, you may be able to send it on again.
The player to your left matters more. In throw-in Durak, your attack is a problem for the defender only. In transfer Durak, an attack you start can land back on you with more cards on the table.
Leading a lone rank becomes safer, because nobody can transfer a rank they do not hold. Low single cards make good opening attacks.
Trying it
The Durak variants page lists transfer Durak alongside other common house rules, and the online game lets you switch it on. Play a few rounds with open hands first so everyone can see what a transfer does.