Sun Titan + Saffi Eriksdotter + sacrifice outlet = infinite sacrifices and ETBs
How it works:
- Sacrifice Saffi Eriksdotter to activate its ability targeting Sun Titan
- Sacrifice Sun Titan, putting the delayed trigger from Saffi Eriksdotter on the stack
- Resolve Saffi Eriksdotter's delayed trigger, returning Sun Titan to the battlefield
- Target Saffi Eriksdotter with Sun Titan's enters the battlefield ability
- Resolve Sun Titan's ETB ability, returning Saffi Eriksdotter to the battlefield
- Repeat