Tom Hiddleston stars as Thor’s adopted brother Loki in the hit Disney+ series, in what is the character’s first solo outing in the Marvel Cinematic Universe (MCU).

Owen Wilson, Gugu Mbatha-Raw and Sophia Di Martino co-star, but there is another main Loki cast member who hasn't shown up yet.

When the series was announced, Richard E. Grant (Star Wars: The Rise of Skywalker) was named among the main cast.

But his role has since been kept tightly under wraps, with no sign of the actor in any of the trailers or episodes so far.

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This has of course sparked fan theories about what exactly his mysterious role could be.

Here are the best predictions so far before the fourth episode.

Who does Richard E. Grant play in Loki?

With no clues from Marvel as to who Richard E. Grant will be playing in the series, fans’ imaginations have been running wild with the possibilities.

Here are some of the best theories:

One of the three Time-Keepers

Most of the action in the first two episodes took place in the Time Variance Authority (TVA), an agency created by the mysterious Time-Keepers to monitor the Sacred Timeline and prevent it from developing into another Multiverse.

Although the Time-Keepers are said to be all-powerful beings running the whole operation, we have yet to see them in the series, with Mobius (Wilson) previously revealing he had also never met them.

With only three episodes left to go, it seems likely that we will get a glimpse of the Time-Keepers soon, so it makes sense that Grant’s role is linked to this upcoming major reveal.

Kang the Conqueror, the villain in the upcoming Ant-Man film, is also highly-anticipated to be another of the Time-Keepers, due to his comic book links to Loki’s Ravonna Renslayer (Mbatha-Raw).

Old Loki

At the end of episode two, Sophia Di Martino made a dramatic entrance as Lady Loki, who we now know as Sylvie, a rogue Loki Variant who had been attacking and killing TVA agents throughout time.

Lots of fans think that Grant’s character will turn out to be Old Loki, another version of the Asgardian God of Mischief, who breached the timeline many years ago.

If this turns out to be true, that would mean there are three versions of Loki in the show, which could lead to a massive showdown at the end of the series to determine which variant remains on the main timeline.

Tom Hiddleston stars in Disney+ series Loki
Tom Hiddleston stars in Disney+ series Loki

A Loki Variant in charge of the Time Variance Authority

This final theory first appeared on Reddit, and combines the previous two ideas, predicting that Grant’s Old Loki is actually the Time-Keeper in charge of the TVA.

There have been some clues that support this theory.

In episode two, Loki made a big deal about being the superior version of himself, mentioning it several times.

Sylvie has also referred to being the better version, showing that this need to be the best is common in all Loki Variants.

Furthermore, Loki’s main plan while in the TVA was to infiltrate the Time-Keepers and take over the TVA.

So what if another version of himself has already achieved this?

If Grant’s character is indeed Old Loki, it’s highly likely that he too will want to reign supreme as the ultimate superior version, so it makes sense that he would have a special interest in eliminating the other versions of himself who may challenge his power.

Or alternatively, he could be looking out for his younger self, in order to continue the cycle of power.

After all, Loki should have been pruned numerous times already, but somehow gets away each time.

When is Loki episode 4 on Disney Plus?

The latest Marvel Studios TV series is at its midway point, with only three episodes left to go.

The fourth episode of Loki will be available to stream on Disney Plus from Wednesday, June 30 at 8am.