Currently, Merlin Chain uses native BTC (Merlin_BTC) as the primary gas token for transaction fees, while MERL can also be used as gas in the AA wallet.
Merlin_BTC
https://docs.merlinchain.io/merlin-docs/user-quick-start/how-to/gas/merlin_btc
MERL (AA Wallet)
https://docs.merlinchain.io/merlin-docs/user-quick-start/how-to/gas/merl-aa-wallet