I was curious what could and could not go through Fiend's Gate and tested a few things. I am sure these existed before Underlord had his ult replaced but I haven't seen a post about it before.
- Enemies can go through gate. Saw this on Insania's stream.
- Illusions can't (Manta, CK, Naga, etc.)
- Beastmaster boar can
- Brewlings can't
- Lycan in ult form and his wolves can
- Phoenix casting sunray can
- Rooted enemies cannot. Includes things like phoinex egg and Nyx burrow
- Arc Warden double can
- Broodmother spiderlings can
- Lone druid bear can't
- Meepo clones can
- Chen creeps cannot
- Dark willow in shadow realm can
- Slark in ult can
- Leashes work as expected. Break on other side. Puck dream coil will stun. Bat lasso will just break.
- Warlock golem can
- Visage birds can
- NP Treants can
I am sure there is more to test but this is all I could think of initially. Chen, Lone Druid and Brewlings seem like they should be able to go through.
Source: https://www.reddit.com/r/DotA2/comments/t23yg6/some_fiends_gate_interactions/
