({5} magic symbol) available, with an additional ({5} magic symbol) every fourth turn available.
Steps
Activate
Kaya's second loyalty ability by removing two loyalty counters from it, causing you to double any tokens you create this turn.
Activate
Osgir by paying ({5} magic symbol) , tapping it and exiling
Ugin's Nexus from your graveyard, creating four token copies of
Ugin's Nexus.
Put three of the
Ugin's Nexus tokens into exile due to the legend rule and their replacement effects, causing you to take three extra turns after this one.
Activate
Karn's first loyalty ability by putting a loyalty counter on it, choosing to do nothing.
Move to your next extra turn.
Activate
Kaya's first loyalty ability by putting a loyalty counter on it, giving creatures you control deathtouch until end of turn and putting a +1/+1 counter on a creature token you control.
Repeat from step 4 one additional time.
Activate
Karn's second loyalty ability by removing two loyalty counters from it, returning