To create an arbitrage triangle on the RICHAMSTER exchange, where there is a KRB-XMR (Karbo to Monero) pair, you need to add another cryptocurrency that is traded on both pairs (with KRB and XMR). For example, you can add **USDT** (Tether) or another popular stablecoin pair:

1. **KRB-USDT**.
2. **XMR-USDT**.

This option will allow you to create an arbitrage triangle:
1. Exchange **KRB for XMR**.
2. Exchange **XMR for USDT**.
3. Exchange **USDT back to KRB**.

Popular stablecoins such as USDT or USDC are commonly used for such transactions as they are available on most exchanges and have a stable exchange rate, which facilitates arbitrage.